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108-627: There were three EarthScope project observatories: These observatories consisted of boreholes into an active fault zone, global positioning system (GPS) receivers, tiltmeters , long-baseline laser strainmeters , borehole strainmeters, permanent and portable seismometers , and magnetotelluric stations. The various EarthScope components provided integrated and highly accessible data on geochronology and thermochronology , petrology and geochemistry , structure and tectonics , surficial processes and geomorphology , geodynamic modeling, rock physics , and hydrogeology . USArray, managed by IRIS,

216-458: A geotechnical investigation or environmental site assessment (a so-called Phase II ESA). This includes holes advanced to collect soil samples, water samples or rock cores, to advance in situ sampling equipment, or to install monitoring wells or piezometers . Samples collected from boreholes are often tested in a laboratory to determine their physical properties, or to assess levels of various chemical constituents or contaminants. Typically,

324-444: A geotechnical investigation , environmental site assessment , mineral exploration , temperature measurement, as a pilot hole for installing piers or underground utilities, for geothermal installations, or for underground storage of unwanted substances, e.g. in carbon capture and storage . Engineers and environmental consultants use the term borehole to collectively describe all of the various types of holes drilled as part of

432-484: A DEM can be used in conjunction with the baseline data to simulate the contribution of the topography to the interferometric phase, this can then be removed from the interferogram. Once the basic interferogram has been produced, it is commonly filtered using an adaptive power-spectrum filter to amplify the phase signal. For most quantitative applications the consecutive fringes present in the interferogram will then have to be unwrapped , which involves interpolating over

540-438: A better understanding of continental deformation. A few questions EarthScope addressed include: Earth's continents are compositionally distinct from the oceanic crust. The continents record four billion years of geologic history, while the oceanic crust gets recycled about every 180 million years. Because of the age of continental crusts, the ancient structural evolution of the continents can be studied. Data from EarthScope

648-622: A bibliometric study on the trends in publications related to landslides and InSAR. They found that the publication trends follow a power model, indicating that despite its inception in the last century, InSAR is a growing topical issue and has become established as a valuable tool for studying landslides. Glacial motion and deformation have been successfully measured using satellite interferometry. The technique allows remote, high-resolution measurement of changes in glacial structure, ice flow, and shifts in ice dynamics, all of which agree closely with ground observations. InSAR can also be used to monitor

756-442: A borehole used as a water well is completed by installing a vertical pipe (casing) and well screen to keep the borehole from caving. This also helps prevent surface contaminants from entering the borehole and protects any installed pump from drawing in sand and sediment. Oil and natural gas wells are completed in a similar, albeit usually more complex, manner. As detailed in proxy (climate) , borehole temperature measurements at

864-547: A few to several hundred boreholes, and in practice, depths have ranged from 50 to 300 metres (150 to 1,000 ft). Borehole drilling has a long history. By at least the Han dynasty (202 BC – 220 AD), the Chinese used deep borehole drilling for mining and other projects. The British sinologist and historian Michael Loewe states that borehole sites could reach as deep as 600 metres (2,000 ft). K.S. Tom describes

972-630: A global scale and on a six-day repeat cycle. Airborne InSAR data acquisition systems are built by companies such as the American Intermap , the German AeroSensing , and the Brazilian OrbiSat . Terrestrial or ground-based SAR interferometry (TInSAR or GBInSAR) is a remote sensing technique for the displacement monitoring of slopes, rock scarps, volcanoes, landslides, buildings, infrastructures etc. This technique

1080-540: A ground motion hazard information service, distributed throughout Europe via national geological surveys and institutions. The objective of this service is to help save lives, improve safety, and reduce economic loss through the use of state-of-the-art PSI information. Over the last 9 years this service has supplied information relating to urban subsidence and uplift, slope stability and landslides, seismic and volcanic deformation, coastlines and flood plains. The processing chain used to produce interferograms varies according to

1188-573: A large amount of information which will contribute to the understanding of continental dynamics and for the quantification of seismic hazards. There were seven topics the EarthScope program addressed with the use of the observatories. Convergent margins, also known as convergent boundaries , are active regions of deformation between two or more tectonic plates colliding with one another. Convergent margins create areas of tectonic uplift , such as mountain ranges or volcanoes. EarthScope focused on

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1296-738: A more detailed insight into faulting and earthquakes than ever before. This project provided a much needed data upgrade from work done in previous years thanks to many technological advances. New data enabled an improved study and understanding of faults and earthquakes that increased our knowledge of the complete earthquake process, allowing for the continued development of building predictive models. Detailed information on internal fault zone architecture, crust and upper mantle structure, strain rates, and transitions between fault systems and deformation types; as well as heat flow, electromagnetic/magnetotelluric, and seismic waveform data, were all made available. A few questions EarthScope addressed include: Through

1404-660: A new multi-image approach in which one searches the stack of images for objects on the ground providing consistent and stable radar reflections back to the satellite. These objects could be the size of a pixel or, more commonly, sub-pixel sized, and are present in every image in the stack. That specific implementation is patented. Some research centres and companies, were inspired to develop variations of their own algorithms which would also overcome InSAR's limitations. In scientific literature, these techniques are collectively referred to as persistent scatterer interferometry or PSI techniques. The term persistent scatterer interferometry (PSI)

1512-405: A number of whole wavelengths plus some fraction of a wavelength. This is observable as a phase difference or phase shift in the returning wave. The total distance to the satellite (i.e., the number of whole wavelengths) is known based on the time that it takes for the energy to make the round trip back to the satellite—but it is the extra fraction of a wavelength that is of particular interest and

1620-584: A prototype of a system that was used to address several key elements of the production of EarthScope products. One of the prototype systems was the receiver reference model. It provided crustal thickness and average crustal Vp/Vs ratios beneath USArray transportable array stations. The main function of the Advanced National Seismic System (ANSS) and USArray, was to provide high quality data for earthquake monitoring, source studies and Earth structure research. The utility of seismic data

1728-467: A regular difference in phase that changes smoothly across the interferogram and can be modelled and removed. The slight difference in satellite position also alters the distortion caused by topography , meaning an extra phase difference is introduced by a stereoscopic effect. The longer the baseline, the smaller the topographic height needed to produce a fringe of phase change – known as the altitude of ambiguity . This effect can be exploited to calculate

1836-698: A remote-sensing technique, and PBO (Plate Boundary Observatory), a fixed array of GPS receivers and strainmeters, the EarthScope project provided spatially continuous strain measurements over wide geographic areas with decimeter to centimeter resolution. The Global Strain Rate Map (GSRM) is a project of the International Lithosphere Program whose mission is to determine a globally self-consistent strain rate and velocity field model, consistent with geodetic and geologic field observations collected by GPS, seismometers, and strainometers. GSRM

1944-915: A salt solution to improve conductivity with the ground. The Plate Boundary Observatory PBO consisted of a series of geodetic instruments, Global Positioning System (GPS) receivers and borehole strainmeters, that were installed to help understand the boundary between the North American Plate and Pacific Plate . The PBO network included several major observatory components: a network of 1100 permanent, continuously operating Global Positioning System (GPS) stations, many of which provide data at high-rate and in real-time, 78 borehole seismometers , 74 borehole strainmeters, 26 shallow borehole tiltmeters, and six long baseline laser strainmeters. These instruments were complemented by InSAR ( interferometric synthetic aperture radar ) and LiDAR ( light detection and ranging ) imagery and geochronology acquired as part of

2052-484: A series of different depths can be effectively " inverted " (a mathematical formula to solve a matrix equation) to help estimate historic surface temperatures. Clusters of small-diameter boreholes equipped with heat exchangers made of plastic PEX pipe can be used to store heat or cold between opposing seasons in a mass of native rock. The technique is called seasonal thermal energy storage . Media that can be used for this technique ranges from gravel to bedrock. There can be

2160-409: A small incidence angle this measures vertical motion well, but is insensitive to horizontal motion perpendicular to the line of sight (approximately north–south). It also means that vertical motion and components of horizontal motion parallel to the plane of the line of sight (approximately east–west) cannot be separately resolved. One fringe of phase difference is generated by a ground motion of half

2268-476: A spatially dense set of seismic recordings, these signals could also be used to visualize the actual continuous seismic waves, providing new insights and interpretation techniques into complex wave propagation effects. Using signals recorded by the array of seismometers, the EarthScope project animated seismic waves as they sweep across the USArray transportable array for selected larger earthquakes. This illustrated

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2376-771: A variety of causes has been successfully measured using InSAR, in particular subsidence caused by oil or water extraction from underground reservoirs, subsurface mining and collapse of old mines. Thus, InSAR has become an indispensable tool to satisfactorily address many subsidence studies. Tomás et al. performed a cost analysis that allowed to identify the strongest points of InSAR techniques compared with other conventional techniques: (1) higher data acquisition frequency and spatial coverage; and (2) lower annual cost per measurement point and per square kilometre. Although InSAR technique can present some limitations when applied to landslides, it can also be used for monitoring landscape features such as landslides . Tomás et al. conducted

2484-657: Is a radar technique used in geodesy and remote sensing . This geodetic method uses two or more synthetic aperture radar (SAR) images to generate maps of surface deformation or digital elevation , using differences in the phase of the waves returning to the satellite or aircraft. The technique can potentially measure millimetre-scale changes in deformation over spans of days to years. It has applications for geophysical monitoring of natural hazards, for example earthquakes, volcanoes and landslides, and in structural engineering , in particular monitoring of subsidence and structural stability . Synthetic aperture radar (SAR)

2592-523: Is a digital model of the global velocity gradient tensor field associated with the accommodation of present-day crustal motions. The overall mission also includes: (1) contributions of global, regional, and local models by individual researchers; (2) archive existing data sets of geologic, geodetic, and seismic information that can contribute toward a greater understanding of strain phenomena; and (3) archive existing methods for modeling strain rates and strain transients. A completed global strain rate map provided

2700-410: Is a form of radar in which sophisticated processing of radar data is used to produce a very narrow effective beam. It can be used to form images of relatively immobile targets; moving targets can be blurred or displaced in the formed images. SAR is a form of active remote sensing – the antenna transmits radiation that is reflected from the image area, as opposed to passive sensing, where the reflection

2808-635: Is an application already in use. In fact, the Federal Emergency Management Agency (FEMA) has awarded the Arizona Geological Survey and its partner universities funding to adopt and maintain eight Transportable Array stations. The stations will be used to update Arizona's earthquake risk assessment. For EarthScope to live up to its potential in the Earth sciences , the connections between the research and

2916-399: Is based on the same operational principles of the satellite SAR interferometry, but the synthetic aperture of the radar (SAR) is obtained by an antenna moving on a rail instead of a satellite moving around an orbit. SAR technique allows 2D radar image of the investigated scenario to be achieved, with a high range resolution (along the instrumental line of sight) and cross-range resolution (along

3024-405: Is consistent – provided nothing on the ground changes the contributions from each target should sum identically each time, and hence be removed from the interferogram. Once the ground effects have been removed, the major signal present in the interferogram is a contribution from orbital effects. For interferometry to work, the satellites must be as close as possible to the same spatial position when

3132-476: Is detected from ambient illumination. SAR image acquisition is therefore independent of natural illumination and images can be taken at night. Radar uses electromagnetic radiation at microwave frequencies; the atmospheric absorption at typical radar wavelengths is very low, meaning observations are not prevented by cloud cover. SAR makes use of the amplitude and the absolute phase of the return signal data. In contrast, interferometry uses differential phase of

3240-407: Is further constrained by baseline criteria. Availability of a suitable DEM may also be a factor for two-pass InSAR; commonly 90 m SRTM data may be available for many areas, but at high latitudes or in areas of poor coverage alternative datasets must be found. A fundamental requirement of the removal of the ground signal is that the sum of phase contributions from the individual targets within

3348-462: Is greatly increased when noise levels, unwanted vibrations, are reduced; however broadband seismograms will always contain a certain level of noise. The dominant sources of noise are either from the instrumentation itself or from ambient Earth vibrations. Normally, seismometer self noise will be well below the seismic noise level, and every station will have a characteristic noise pattern that can be calculated or observed. Sources of seismic noise within

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3456-407: Is measured to great accuracy. In practice, the phase of the return signal is affected by several factors, which together can make the absolute phase return in any SAR data collection essentially arbitrary, with no correlation from pixel to pixel. To get any useful information from the phase, some of these effects must be isolated and removed. Interferometry uses two images of the same area taken from

3564-699: Is the change in shape and volume of continental and oceanic crust caused by stress applied to rock through tectonic forces. An array of variables including composition, temperature, pressure, etc., determines how the crust will deform. A few questions EarthScope addressed include: Continental deformation is driven by plate interactions through active tectonic processes such as continental transform systems with extensional, strike-slip, and contractional regimes. EarthScope provided velocity field data, portable and continuous GPS data, fault-zone drilling and sampling, reflection seismology, modern seismicity, pre- Holocene seismicity, and magnetotelluric and potential field data for

3672-510: Is the electromagnetic equivalent of the seismic arrays. The portable sensors were moved in a rolling grid similar to the Transportable Array grid, but were only in place about a month before they were moved to the next location. A magnetotelluric station consists of a magnetometer , four electrodes , and a data recording unit that are buried in shallow holes. The electrodes are oriented north-south and east-west and are saturated in

3780-409: The three-pass method two images acquired a short time apart are used to create an interferogram, which is assumed to have no deformation signal and therefore represent the topographic contribution. This interferogram is then subtracted from a third image with a longer time separation to give the residual phase due to deformation. Once the ground, orbital and topographic contributions have been removed

3888-443: The 0 to 2π phase jumps to produce a continuous deformation field. At some point, before or after unwrapping, incoherent areas of the image may be masked out. The final processing stage involves geocoding the image, which resamples the interferogram from the acquisition geometry (related to direction of satellite path) into the desired geographic projection . Early exploitation of satellite-based InSAR included use of Seasat data in

3996-664: The 1980s, but the potential of the technique was expanded in the 1990s, with the launch of ERS-1 (1991), JERS-1 (1992), RADARSAT-1 and ERS-2 (1995). These platforms provided the stable, well-defined orbits and short baselines necessary for InSAR. More recently, the 11-day NASA STS-99 mission in February 2000 used a SAR antenna mounted on the Space Shuttle to gather data for the Shuttle Radar Topography Mission (SRTM). In 2002 ESA launched

4104-682: The ASAR instrument, designed as a successor to ERS, aboard Envisat . While the majority of InSAR to date has utilized the C-band sensors, recent missions such as the ALOS PALSAR , TerraSAR-X and COSMO-SkyMed are expanding the available data in the L- and X-band. Sentinel-1A and Sentinel-1B , both C-band sensors, were launched by the ESA in 2014 and 2016, respectively. Together, they provide InSAR coverage on

4212-490: The Earth are caused by any of the following: the actions of human beings at or near the surface of the Earth, objects moved by wind with the movement being transferred to the ground, running water (river flow), surf, volcanic activity, or long period tilt due to thermal instabilities from poor station design. A new approach to seismic noise studies was introduced with the EarthScope project, in that there were no attempts to screen

4320-483: The Earth sciences community. Invigoration is self-perpetuating as evidenced by participation from thousands of organizations from around the world and from all levels of students and researchers. This leads to a significantly heightened awareness within the general public, including the next cohort of prospective Earth scientists. With further evolution of the EarthScope project, there were opportunities to create new observatories with greater capabilities, including extending

4428-540: The Earth. The Reference Network was composed of permanent seismic stations spaced about 300 km apart. The Reference Network provided a baseline for the Transportable Array and Flexible Array. EarthScope added and upgraded 39 stations to the already existing Advanced National Seismic System , which was part of the Reference Network. The Magnetotelluric Facility was composed of seven permanent and 20 portable sensors that recorded electromagnetic fields . It

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4536-736: The EarthScope project. The arrays included the Pacific Northwest Geodetic Array, EarthScope's Plate Boundary Observatory, the Western Canadian Deformation Array, and networks run by the US Geological Survey. The daily GPS measurements from ~1500 stations along the Pacific/North American plate boundary provided millimeter-scale accuracy and could be used monitor the displacements of the earths crust. With

4644-474: The GeoEarthScope initiative. PBO also included comprehensive data products, data management and education and outreach efforts. These permanent networks were supplemented by a pool of portable GPS receivers that could be deployed for temporary networks to researchers, to measure the crustal motion at a specific target or in response to a geologic event. The Plate Boundary Observatory portion of EarthScope

4752-612: The Russian island Sakhalin . The Chayvo Z-44 extended-reach well took the title of the world's longest borehole on 27 August 2012. Z-44's total measured depth is 12,376 metres (40,604 ft). However, ERD wells are more shallow than the Kola Borehole, owing to a large horizontal displacement. In July 2023, China began drilling deep boreholes, one at the Sichuan Basin expected to reach 10,520 metres (34,510 ft) into

4860-581: The U.S. came from USArray transportable array and Advance National Seismic System broadband seismic stations. Results were obtained in the time and the frequency domain. Waveform fit and amplitude-phase match figures were provided to allow users to evaluate moment tensor quality. Global Positioning System (GPS) equipment and techniques provide a unique opportunity for earth scientists to study regional and local tectonic plate motions and conduct natural hazards monitoring. Cleaned network solutions from several GPS arrays merged into regional clusters in conjunction with

4968-461: The USArray over the Gulf of Mexico and the Gulf of California . There is much promise for EarthScope tools and observatories, even after retirement, to be used by universities and professional geologists . These tools include the physical equipment, software invented to analyze the data, and other data and educational products initiated or inspired by EarthScope. The science produced by EarthScope and

5076-437: The absolute movement of a point. A variety of factors govern the choice of images which can be used for interferometry. The simplest is data availability – radar instruments used for interferometry commonly don't operate continuously, acquiring data only when programmed to do so. For future requirements it may be possible to request acquisition of data, but for many areas of the world archived data may be sparse. Data availability

5184-522: The atmosphere was horizontally homogeneous over the length scale of an interferogram and vertically over that of the topography then the effect would simply be a constant phase difference between the two images which, since phase difference is measured relative to other points in the interferogram, would not contribute to the signal. However, the atmosphere is laterally heterogeneous on length scales both larger and smaller than typical deformation signals. This spurious signal can appear completely unrelated to

5292-508: The borehole is lined with materials like bricks, stones, or concrete rings. This reinforcement maintains the integrity of the borehole's structure and helps to prevent contamination. A concrete platform or slab may be installed at the bottom to prevent sediment from entering the water. The top of the borehole is capped to protect it from debris and contamination. Interferometric synthetic aperture radar Interferometric synthetic aperture radar , abbreviated InSAR (or deprecated IfSAR ),

5400-569: The boundary between the Pacific Plate and the North American Plate in the western United States. EarthScope provided GPS geodetic data, seismic images, detailed seismicity, magnetotelluric data, InSAR , stress field maps, digital elevation models , baseline geology, and paleoseismology for a better understanding of convergent margin processes. A few questions EarthScope addressed include: Crustal strain and deformation

5508-431: The classroom. Their job was to make sure that everyone understood what EarthScope was, what it was doing in the community, and how to use the data it was producing. By generating new research opportunities for students in the scientific community, the program also hoped to expand recruitment for future generations of earth scientists. "To use EarthScope data, products, and results to create a measurable and lasting change on

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5616-446: The continuous waveforms to eliminate body and surface waves from the naturally occurring earthquakes. Earthquake signals are not generally included in the processing of noise data, because they are generally low probability occurrences, even at low power levels. The two objectives behind the collection of the seismic noise data were to provide and document a standard method to calculate ambient seismic background noise, and to characterize

5724-420: The contributions to the phase within each pixel, for example changes to the ground targets in each pixel caused by vegetation growth, landslides, agriculture or snow cover. Another source of error present in most interferograms is caused by the propagation of the waves through the atmosphere. If the wave travelled through vacuum, it should theoretically be possible (subject to sufficient accuracy of timing) to use

5832-537: The country. Building an Earth model of this scale required a complex community effort, and this model is largely the first EarthScope legacy. Researchers analyzing the data left us with a greater scientific understanding of geologic resources in the Great Basin and of the evolution of the plate boundary on the North American west coast. Another geologic legacy desired by the initiative, was to invigorate

5940-454: The creativity of those who wish to sort through the gigabytes of data. Also, because of its scale, the program will undoubtedly be the topic of casual conversation for many people outside of the geologic community. EarthScope chatter will be made by people in political, educational, social, and scientific arenas. The multidisciplinary character of EarthScope helped create stronger network connections between geologists of all types and from around

6048-447: The deep Earth and how the evolution of continental lithosphere is related to upper mantle processes. The basic idea of how the various melts are formed is known, but not the volumes and rates of magma production outside of Mid-ocean ridge basalts . EarthScope provided seismic data and tomographic images of the mantle to better understand these processes. A few questions EarthScope addressed include: The Education and Outreach Program

6156-608: The drilling process: "The Chinese method of deep drilling was accomplished by a team of men jumping on and off a beam to impact the drilling bit while the boring tool was rotated by buffalo and oxen." This was the same method used for extracting petroleum in California during the 1860s (i.e. "kicking her down"). A Western Han dynasty bronze foundry discovered in Xinglong, Hebei had nearby mining shafts which reached depths of 100 metres (330 ft) with spacious mining areas;

6264-425: The drilling rig. Especially in developing countries many boreholes are stull dug by hand. The digging begins with manual labor using basic tools such as shovels, picks, and crowbars. Workers excavate the soil layer by layer, often using a circular motion to create a well-shaped hole. The process is slow and demanding, requiring teamwork and coordination. To prevent the walls from collapsing and to ensure water quality,

6372-483: The education and outreach communities must continue to be cultivated. Enhanced public outreach to museums, the National Park System , and public schools will ensure that these forward-thinking connections are fostered. National media collaboration with high-profile outlets such as Discovery Channel , Science Channel , and National Geographic may secure a lasting legacy within the social consciousness of

6480-544: The effects on the passage of energy waves impinging on those structures. The waves of energy are P-waves generated by earthquakes and are recording the wave velocities. The high quality data that was collected by the permanent seismic stations of USArray and the Advanced National Seismic System (ANSS) allowed the creation of high resolution seismic imaging of the Earth's interior below the United States. Seismic tomography helps constrain mantle velocity structure and aids in

6588-455: The field developed. The technique is now widely used for academic research into volcanic deformation, although its use as an operational monitoring technique for volcano observatories has been limited by issues such as orbital repeat times, lack of archived data, coherence and atmospheric errors. Recently InSAR has been used to study rifting processes in Ethiopia. Ground subsidence from

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6696-476: The ground and the other at the Tarim Basin with a planned depth of 11,100 metres (36,400 ft). Drillers may sink a borehole using a drilling rig or a hand-operated rig. The machinery and techniques to advance a borehole vary considerably according to manufacturer, geological conditions, and the intended purpose. For offshore drilling floating units or platforms supported by the seafloor are used for

6804-450: The ground surface. The phase of the wave may change on reflection , depending on the properties of the material. The reflected signal back from any one pixel is the summed contribution to the phase from many smaller 'targets' in that ground area, each with different dielectric properties and distances from the satellite, meaning the returned signal is arbitrary and completely uncorrelated with that from adjacent pixels. Importantly though, it

6912-620: The holes varied, the drilling of a single well could last nearly one full decade. It was not up until the 19th century that Europe and the West would catch up and rival ancient Chinese borehole drilling technology. For many years, the world's longest borehole was the Kola Superdeep Borehole in Russia. From 2011 until August 2012 the record was held by the 12,345-metre (40,502 ft) long Sakhalin-I Odoptu OP-11 Well, offshore

7020-411: The images are acquired. This means that images from two satellite platforms with different orbits cannot be compared, and for a given satellite data from the same orbital track must be used. In practice the perpendicular distance between them, known as the baseline , is often known to within a few centimetres but can only be controlled on a scale of tens to hundreds of metres. This slight difference causes

7128-440: The interferogram contains the deformation signal, along with any remaining noise (see Difficulties below). The signal measured in the interferogram represents the change in phase caused by an increase or decrease in distance from the ground pixel to the satellite, therefore only the component of the ground motion parallel to the satellite line of sight vector will cause a phase difference to be observed. For sensors like ERS with

7236-425: The moment tensor magnitude, is the most reliable quantity for comparing and measuring the size of an earthquake with other earthquake magnitudes. Moment tensors are used in a wide range of seismological research fields, such as earthquake statistics, earthquake scaling relationships, and stress inversion. The creation of regional moment tensor solutions, with the appropriate software, for moderate-to-large earthquakes in

7344-429: The name EarthScope Consortium to represent the shared vision of the new organization. Boreholes A borehole is a narrow shaft bored in the ground, either vertically or horizontally. A borehole may be constructed for many different purposes, including the extraction of water ( drilled water well and tube well ), other liquids (such as petroleum ), or gases (such as natural gas ). It may also be part of

7452-482: The nature of the major tectonic features. This method gives evidence for differences in thickness and the velocity anomaly of the mantle lithosphere between the stable center of the continent and the more active western North America. These data are vital for the understanding of local lithosphere evolution, and when combined with additional global data, allow the mantle to be imaged beyond the current extent of USArray. EarthScope Automated Receiver Survey (EARS), created

7560-406: The physical processes controlling earthquakes and volcanoes. The goal of USArray was primarily to gain a better understanding of the structure and evolution of the continental crust , lithosphere , and mantle underneath North America. The USArray was composed of four facilities: a Transportable Array, a Flexible Array, a Reference Network, and a Magnetotelluric Facility. The Transportable Array

7668-446: The pixel remains constant between the two images and is completely removed. However, there are several factors that can cause this criterion to fail. Firstly the two images must be accurately co-registered to a sub-pixel level to ensure that the same ground targets are contributing to that pixel. There is also a geometric constraint on the maximum length of the baseline – the difference in viewing angles must not cause phase to change over

7776-495: The processes that control the behavior of the San Andreas Fault. Data collected from the various observatories were used to create different types of data products. Each data product addressed a different scientific problem. Tomography is a method of producing a three-dimensional image of the internal structures of a solid object (such as the human body or the earth) by the observation and recording of differences in

7884-461: The professors, but their students as well. Scouting for future seismic station locations created field work opportunities for students. The influx of data helped creaate projects for undergraduate research, master's thesis, and doctoral dissertations. A list of funded proposals can be found on the NSF website. Many applications for EarthScope data currently exist, as mentioned above. The EarthScope program

7992-416: The radar wavelength, since this corresponds to a whole wavelength increase in the two-way travel distance. Phase shifts are only resolvable relative to other points in the interferogram. Absolute deformation can be inferred by assuming one area in the interferogram (for example a point away from expected deformation sources) experienced no deformation, or by using a ground control ( GPS or similar) to establish

8100-410: The reflected radiation, either from multiple passes along the same trajectory and/or from multiple displaced phase centers (antennas) on a single pass. Since the outgoing wave is produced by the satellite, the phase is known, and can be compared to the phase of the return signal. The phase of the return wave depends on the distance to the ground, since the path length to the ground and back will consist of

8208-443: The regional and teleseismic wave propagation phenomena. The seismic data collected from both permanent and transportable seismic stations was used to provide these computer generated animations. The seismic moment tensor is one of the fundamental parameters of earthquakes that can be determined from seismic observations. It is directly related to earthquake fault orientation and rupture direction. The moment magnitude , Mw derived from

8316-565: The researchers using its data products help guide lawmakers in environmental policy, hazard identification, and ultimately, federal funding of more large-scale projects like this one. Besides the three physical dimensions of North America's structure, a fourth dimension of the continent is being described through geochronology using EarthScope data. Improving understanding of the continent's geologic history allow future generations to more efficiently manage and use geologic resources and live with geologic hazards . Environmental policy laws have been

8424-418: The same position (or, for topographic applications, slightly different positions) and finds the difference in phase between them, producing an image known as an interferogram. This is measured in radians of phase difference and, because of the cyclic nature of phase, is recorded as repeating fringes that each represent a full 2π cycle. The most important factor affecting the phase is the interaction with

8532-629: The scan direction). Two antennas respectively emit and receive microwave signals and, by calculating the phase difference between two measurements taken in two different times, it is possible to compute the displacement of all the pixels of the SAR image. The accuracy in the displacement measurement is of the same order of magnitude as the EM wavelength and depends also on the specific local and atmospheric conditions. InSAR can be used to measure tectonic deformation, for example ground movements due to earthquakes . It

8640-411: The shafts and rooms were complete with a timber frame, ladders and iron tools. By the first century BC, Chinese craftsmen cast iron drill bits and drillers were able to drill boreholes up to 1,500 metres (4,900 ft) deep. By the eleventh century AD, the Chinese were able to drill boreholes up to 900 metres (3,000 ft) in depth. Drilling for boreholes was time-consuming and long. As the depth of

8748-404: The software used and the precise application but will usually include some combination of the following steps. Two SAR images are required to produce an interferogram; these may be obtained pre-processed, or produced from raw data by the user prior to InSAR processing. The two images must first be co-registered , using a correlation procedure to find the offset and difference in geometry between

8856-452: The source of forces originating in the upper mantle and their effects on the continental lithosphere. Seismic data gave scientists more understanding and insight into the lower mantle and the Earth's core, as well as activity at the core-mantle boundary . A few questions hoping to be answered by EarthScope included: EarthScope hoped to provide a better understanding of the physics of fluids and magmas in active volcanic systems in relation to

8964-544: The stability of built structures. Very high resolution SAR data (such as derived from the TerraSAR-X StripMap mode or COSMO-Skymed HIMAGE mode) are especially suitable for this task. InSAR is used for monitoring highway and railway settlements, dike stability, forensic engineering and many other uses. Interferograms can be used to produce digital elevation maps (DEMs) using the stereoscopic effect caused by slight differences in observation position between

9072-621: The subject of some controversy since the European settlement of North America. Specifically, water and mineral rights issues have been the focus of dispute. Representatives in Washington D.C. and the state capitals require guidance from authoritative science in drafting the soundest environmental laws for our country. The EarthScope research community was in a position to provide the most reliable course for government to take concerning environmental policy. Hazard identification with EarthScope

9180-474: The surface features of the image, however, in other cases the atmospheric phase delay is caused by vertical inhomogeneity at low altitudes and this may result in fringes appearing to correspond with the topography. Persistent or permanent scatterer techniques are a relatively recent development from conventional InSAR, and rely on studying pixels which remain coherent over a sequence of interferograms. In 1999, researchers at Politecnico di Milano , Italy, developed

9288-408: The topographic height, and used to produce a digital elevation model (DEM). If the height of the topography is already known, the topographic phase contribution can be calculated and removed. This has traditionally been done in two ways. In the two-pass method, elevation data from an externally derived DEM is used in conjunction with the orbital information to calculate the phase contribution. In

9396-401: The two amplitude images. One SAR image is then re-sampled to match the geometry of the other, meaning each pixel represents the same ground area in both images. The interferogram is then formed by cross-multiplication of each pixel in the two images, and the interferometric phase due to the curvature of the Earth is removed, a process referred to as flattening. For deformation applications

9504-399: The two images. When using two images produced by the same sensor with a separation in time, it must be assumed other phase contributions (for example from deformation or atmospheric effects) are minimal. In 1995 the two ERS satellites flew in tandem with a one-day separation for this purpose. A second approach is to use two antennas mounted some distance apart on the same platform, and acquire

9612-401: The two-way travel-time of the wave in combination with the phase to calculate the exact distance to the ground. However, the velocity of the wave through the atmosphere is lower than the speed of light in vacuum, and depends on air temperature, pressure and the partial pressure of water vapour. It is this unknown phase delay that prevents the integer number of wavelengths being calculated. If

9720-402: The understanding of chemical and geodynamic processes that are at work. With the use of the data collected by USArray and global travel-time data, a global tomography model of P-wave velocity heterogeneity in the mantle could be created. The range and resolution of this technique allowed investigation into the suite of problems that are of concern in the North American mantle lithosphere, including

9828-427: The use of data modeling software and the recorded GPS data, the opportunity to quantify crustal deformation caused by plate tectonics , earthquakes, landslides and volcanic eruptions was possible. The goal was to provide models of time-dependent strain associated with a number of recent earthquakes and other geologic events as constrained by GPS data. With the use of InSAR (Interferometric Synthetic Aperture Radar),

9936-438: The use of seismology, scientists were be able to collect and evaluate data from the deepest parts of our planet, from the continental lithosphere down to the core. The relationship between lithospheric and the upper mantle processes is something that is not completely known, including upper mantle processes below the United States and their effects on the continental lithosphere. There are many issues of interest, such as determining

10044-402: The use of this new method it became much easier to compare seismic noise characteristics between different networks in different regions. Seismometers of USArray transportable array recorded the passage of numerous seismic waves through a given point near the Earth's surface, and classically these seismograms are analyzed to deduce properties of the Earth's structure and the seismic source. Given

10152-640: The user could add various types of base maps, features, and plate velocities. Educators could access to real time GPS data of plate movement and influences through the UNAVCO website. EarthScope promised to produce a large amount of geological and geophysical data to the door for numerous research opportunities in the scientific community. As the USArray Big Foot project moved across the country, universities adopted seismic stations near their areas. These stations were then monitored and maintained by not only

10260-420: The variation of ambient background seismic noise levels across the United States as a function of geography , season, and time of day. The new statistical approach provided the ability to compute probability density functions (PDFs) to evaluate the full range of noise at a given seismic station, allowing the estimation of noise levels over a broad range of frequencies from 0.01–16 Hz (100-0.0625s period). With

10368-412: The way that Earth science is taught and perceived in the United States." Education and outreach developed tools for educators and students across the United States to interpret and apply this information for solving a wide range of scientific issues within the earth sciences. The project tailored its products to the specified needs and requests of educators. The EarthScope Education and Outreach Bulletin

10476-440: The width of one pixel by more than a wavelength. The effects of topography also influence the condition, and baselines need to be shorter if terrain gradients are high. Where co-registration is poor or the maximum baseline is exceeded the pixel phase will become incoherent – the phase becomes essentially random from pixel to pixel rather than varying smoothly, and the area appears noisy. This is also true for anything else that changes

10584-472: The world. Earth science has already been promoted as a vital modern discipline, especially in today's “green” culture, to which EarthScope is contributing. The size of the EarthScope project augments the growing public awareness of the broad structure of the planet on which we live. Given that IRIS and UNAVCO operated the seismology and geodesy components of the instrumentation that the project relied on, when these two organizations merged in 2023 they adopted

10692-443: Was a 15-year program to place a dense network of permanent and portable seismographs across the continental United States. These seismographs recorded the seismic waves released by earthquakes that occur around the world. Seismic waves are indicators of energy disbursement within the earth. By analyzing the records of earthquakes obtained from this dense grid of seismometers, scientists could learn about Earth structure and dynamics and

10800-441: Was a bulletin targeted for grades 5-8 that summarized a volcanic or tectonic event documented by EarthScope and put it into an easily interpretable format, complete with diagrams and 3D models. They followed specific content standards based on what a child should be learning at those grade levels. The EarthScope Voyager, Jr. allowed students to explore and visualize the various types of data that were collected. In this interactive map,

10908-468: Was completed, over 2000 locations had been occupied. The Array Network Facility was responsible for data collection from the Transportable Array stations. The Flexible Array was composed of 291 broadband stations, 120 short period stations, and 1700 active source stations. The Flexible Array allowed sites to be targeted in a more focused manner than the broad Transportable Array. Natural or artificially created seismic waves could be used to map structures in

11016-409: Was composed of 400 seismometers that were deployed in a rolling grid across the United States over a period of 10 years. The stations were placed 70 km apart, and could map the upper 70 km of the Earth. After approximately two years, stations were moved east to the next site on the grid – unless adopted by an organization and made a permanent installation. Once the sweep across the United States

11124-413: Was dedicated to determining the three dimensional structure of the North American continent. Future uses of the data that it produced might include hydrocarbon exploration , aquifer boundary establishment, remote sensing technique development, and earthquake risk assessment. Due to the open and free-to-the-public data portals that EarthScope and its partners maintain, the applications are limited only by

11232-578: Was designed to integrate EarthScope into both the classroom and the community. The program reached out to scientific educators and students as well as industry professionals (engineers, land/resource managers, technical application/data users), partners of the project ( UNAVCO , IRIS, USGS, NASA, etc.), and the general public. To accomplish this, the EOP offered a wide array of educational workshops and seminars, directed at various audiences, to offer support on data interpretation and implementation of data products into

11340-704: Was first used for the 1992 Landers earthquake , but has since been utilised extensively for a wide variety of earthquakes all over the world. In particular the 1999 Izmit and 2003 Bam earthquakes were extensively studied. InSAR can also be used to monitor creep and strain accumulation on faults . InSAR can be used in a variety of volcanic settings, including deformation associated with eruptions , inter-eruption strain caused by changes in magma distribution at depth, gravitational spreading of volcanic edifices, and volcano-tectonic deformation signals. Early work on volcanic InSAR included studies on Mount Etna , and Kilauea , with many more volcanoes being studied as

11448-463: Was operated by UNAVCO . The San Andreas Fault Observatory at Depth (SAFOD) consisted of a main borehole that cut across the active San Andreas Fault at a depth of approximately 3 km and a pilot hole about 2 km southwest of San Andreas Fault. Data from the instruments installed in the holes, which consisted of geophone sensors, data acquisition systems, and GPS clocks, as well as samples collected during drilling, helped to better understand

11556-518: Was proposed by European Space Agency (ESA) to define the second generation of radar interferometry techniques. This term is nowadays commonly accepted by scientific and the end user community. Commonly such techniques are most useful in urban areas with many permanent structures, for example the PSI studies of European geohazard sites undertaken by the Terrafirma project. The Terrafirma project provides

11664-440: Was used to find the mean seismic structure of the continental crust, associated mantle, and crust-mantle transition. Variability in that structure was also studied. EarthScope attempted to define continental lithosphere formation and continent structure and to identify the relationship between continental structure and deformation. A few questions EarthScope addressed include: EarthScope acquired 3D and 4D data that gave scientists

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