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39-758: The WWSSN also "created a global network infrastructure, including the data-exchange procedures and station technical capabilities needed to support the establishment of the more advanced networks in operation today", and has been the model for every global seismic network since then. A principal feature of the WWSSN was that each station had identical equipment, uniformly calibrated. These consisted of three short-period (~1 second) seismographs (oriented north–south, east–west, and vertically), three long-period (~15 seconds) seismographs, and an accurate radio-synchronized crystal-controlled clock. The seismograms were produced on photographic drum recorders, developed on-site, then sent to

78-413: A Data Center for copying onto 70-mm and 35-mm film (until 1978, and then after onto microfiche). The WWSSN also featured a data distribution system that made this data available to anyone at nominal cost from a single location, providing the basis for much research. The WWSSN arose from a political concern. In the 1950s concerns about radioactive fallout from above-ground testing of nuclear weapons prompted

117-406: A broad range of ballistic events. Analog chart recorders using a galvanometer movement to directly drive the pen have limited sensitivity. In a potentiometric type of recorder, the direct drive of the marking pen is replaced with a servomechanism where energy to move the pen is supplied by an amplifier. The motor-operated pen is arranged to move the sliding contact of a potentiometer to feed back

156-417: A continuous reel of film. The signals from seismometers are processed by 15.5 Hz recording galvanometers which record the seismograms to a reel of 200 feet (61 m) of film at the speeds between 3 and 20 centimetres (1.2 and 7.9 in) per minute. The machine has self-contained circulating chemicals that are used to automatically develop the film. However, the machine takes at least ten minutes from

195-431: A direct-reading meter, the recorder deflects a pen or other marking device. The writing mechanism may be a heated needle writing on heat-sensitive paper or a simple hollow ink-fed pen. If the pen is continuously pressed against the paper, the galvanometer must be strong enough to move the pen against the friction of the paper. To lessen the strain on the galvanometer the pen might instead only intermittently be pressed against

234-577: A disposable cartridge combining both a fiber-tipped pen and ink reservoir has been used. Other types of recorder use a heated stylus and thermally sensitive paper, an impact printer using a ribbon and an electrically operated hammer, an electric signal acting through a stylus onto electro-sensitive paper, or an electric spark that makes a visible spot on aluminized paper. One form of sensitive and high-speed recorder used beams of ultraviolet light reflected off mirror galvanometers , directed at light-sensitive paper. The earliest instruments derived power to move

273-401: A hyphen "-" between each minute. Minute marks count minutes on seismograms. From left to right, each mark stands for a minute. Each seismic wave looks different. The P wave is the first wave that is bigger than the other waves (the microseisms ). Because P waves are the fastest seismic waves, they will usually be the first ones that the seismograph records. The next set of seismic waves on

312-450: A kind of chart recorder . Some used pens on ordinary paper, while others used light beams to expose photosensitive paper. Today, practically all seismograms are recorded digitally to make analysis by computer easier. Some drum seismometers are still found, especially when used for public display. Seismograms are essential for finding the location and magnitude of earthquakes. Prior to the availability of digital processing of seismic data in

351-402: A process or to follow process upsets. Medical and scientific recorders allow a wide range of accurately-controlled speeds to be set. An "X-Y" recorder drives the chart depending on the value of another process signal. For example, a universal testing machine may plot the tension force on a specimen against its length. Depending on the particular recorder, either the paper chart is moved or else

390-450: A seismogram may result from an earthquake or from some other source, such as an explosion . Seismograms can record many things, and record many little waves, called microseisms . These tiny events can be caused by heavy traffic near the seismograph, waves hitting a beach, the wind, and any number of other ordinary things that cause some shaking of the seismograph. Historically, seismograms were recorded on paper attached to rotating drums,

429-400: A stationary fiber-optic cathode ray tube that was in direct contact with the paper. These recorders had several flaws. The photo-sensitive paper was very expensive, and would quickly fade when exposed to ambient light. High chart speeds meant that test durations were extremely short. These instruments were intended to capture short-duration events such as NASA rocket launches in the 1960s and

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468-419: Is the only option. The paper chart is driven past the pen at a steady rate by a clockwork or electrical drive mechanism. One common method is to use a miniature synchronous motor which turns at a constant speed related to the power frequency ; a gear-train is used to propel the paper. Industrial strip-chart recorders may have two-speed gear trains that allow a higher speed to be used for initial adjustments of

507-671: The U.S. Coast and Geodetic Survey (C&GS) to implement one of the Berkner Report recommendations, designing and building what became the WWSSN. Performance specifications and a request for proposals were published in November 1960, a contract awarded in early 1961, and the first station was installed in the C&;GS Albuquerque (New Mexico) Seismological Laboratory (ASL) in October 1961. An additional 89 stations were installed by

546-639: The Bristol Manufacturing Company in 1889. The Bristol Company was acquired by Emerson Electric Company in March 2006, and continues to manufacture a number of different electro-mechanical chart recorders, as well as other instrumentation, measurement, and control products. The first chart recorder for environmental monitoring was designed by American inventor J.C. Stevens while working for Leupold & Stevens in Portland, Oregon and

585-547: The Commerce Department were blocked by an impasse in Congress. Though other agencies contributed partial funding (mainly for purchase and shipping of photographic supplies), permanent funding was not obtained, and routine maintenance and training were suspended. In 1973 ASL and WWSSN were transferred to the U.S. Geological Survey (USGS), and operation of the network continued at a reduced level of support until it

624-409: The arc of a circle, making the scale difficult to read; pre-printed charts have curvilinear scales printed on them that compensated for the path of the marking pen. Many types of chart recorders use a galvanometer to drive the marking device. A light coil of wire suspended in the magnetic field of a permanent magnet deflects in proportion to the current through it; instead of the pointer and scale of

663-500: The chart (with mechanical or pressure inputs), or entirely electronic with no mechanical components at all (a virtual chart recorder). Chart recorders are built in three primary formats. Strip chart recorders have a long strip of paper that is ejected out of the recorder. Circular chart recorders have a rotating disc of paper that must be replaced more often, but are more compact and amenable to being enclosed behind glass. Roll chart recorders are similar to strip chart recorders except that

702-468: The dots and dashes of the code, inscribed on a paper tape by a pen moved by an electromagnet, with a clockwork mechanism advancing the paper. In 1848-1850 a system of such registers was used by John Locke to improve the precision of astronomical observations of stars, providing timing precision much greater than previous methods. This method was adopted by astronomers in other countries as well. William Thomson, 1st Baron Kelvin 's syphon recorder of 1858

741-618: The end of 1963, and the network was essentially complete by the end of 1967 with 117 stations, with 121 stations eventually installed. These were mostly outside of the U.S., but not in Canada (they had their own system), the Soviet-bloc countries, China or France (they were building their own nuclear weapons and wanted to retain an option for testing), or French-speaking countries. DARPA funding ended in fiscal year 1967 (July 1966–June 1967), and plans for transferring funding responsibilities to

780-434: The late 1970s, the records were done in a few different forms on different types of media. A Helicorder drum is a device used to record data into photographic paper or in the form of paper and ink. A piece of paper is wrapped around a rotating drum of the helicorder which receives the seismic signal from a seismometer. For each predefined interval of data, the helicorder will plot the seismic data in one line before moving to

819-641: The leadership of the three leading nuclear nations (President Eisenhower of the United States, General Secretary Khrushchev of the Soviet Union, and Prime Minister Macmillan of the United Kingdom) to ban further testing of nuclear weapons. However, there was a hitch. The United States would not agree to banning kinds of nuclear tests where there was no capability to detect and identify any violations, and for smaller, underground tests seismology

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858-399: The long table ... About a dozen pens connected with a bridge crossing the middle of the table were each marking its own independent curve gradually or by jumps ..." The paper advance was geared to the wheels of the railroad carriage, while pens recorded time, the drawbar pull of the locomotive, and numerous other variables. Part of Samuel Morse 's telegraph system was an automatic recorder of

897-469: The next line at the next interval. The paper must be changed after the helicorder writes on the last line of the paper. In the model that use ink, regular maintenance of the pen must be done for accurate recording. A Develocorder is a machine that records multi-channel seismic data into a 16 mm film . The machine was developed by Teledyne Geotech during the mid-1960s. It can automatically plot seismograms from 18 seismic signal sources and 3 time signals on

936-425: The pen carriage has two axes of motion. Examples of an x-y recorder date back to the 18th century in the form of the steam indicator diagrams used to record pressure and volume in steam engines. Many mechanisms have been adopted for marking paper. In the telegraphic siphon recorder of 1858 a fine capillary tube is connected to an ink reservoir and is deflected by the process signal. In modern strip chart recorders,

975-443: The pen directly from the sensed process signal, which limited their sensitivity and speed of response. Friction between the marking device and paper would reduce the accuracy of the measurements. Instruments with pneumatic, mechanical, or electromechanical amplifiers decoupled pen movement from process measurement, greatly increasing the sensitivity of the instrument and the flexibility of the recorder. Directly-driven pens often moved in

1014-399: The pen position to an error amplifier. The amplifier drives the motor in such a direct as to reduce the error between desired and actual pen position to zero. With a suitable signal processing amplifier, such instruments can record a wide range of process signals. However, the inertia of the servo system limits the speed of response, making these instruments most useful for signals changing over

1053-399: The recorded data is stored on a round roll, and the unit is usually fully enclosed. Chart recorders pre-dated electronic data loggers which have replaced them in many applications. Charles Babbage incorporated a chart recorder into the dynamometer car that he built in 1838 or 1839. Here is how he described it: "A roll of paper a thousand feet in length was slowly unwinding itself upon

1092-605: The seismogram will be the S waves . These are usually bigger than the P waves, and have higher frequency. Look for a dramatic change in frequency for a different type of wave. Chart recorder A chart recorder is an electromechanical device that records an electrical or mechanical input trend onto a piece of paper (the chart). Chart recorders may record several inputs using different color pens and may record onto strip charts or circular charts. Chart recorders may be entirely mechanical with clockwork mechanisms, electro-mechanical with an electrical clockwork mechanism for driving

1131-411: The seismograms into digital medias. Seismograms are read from left to right. Time marks show when the earthquake occurred. Time is shown by half-hour (thirty-minute) units. Each rotation of the seismograph drum is thirty minutes. Therefore, on seismograms, each line measures thirty minutes. This is a more efficient way to read a seismogram. Secondly, there are the minute-marks. A minute mark looks like

1170-675: The span of a second or more. A modern chart recorder is an embedded computer system with an analog-to-digital converter , a microcontroller , and a hard-copy printing device; such instruments allow great flexibility in signal processing, variable chart speed on process upsets, and can also communicate their measurements to remote points. One of the first digital units was designed by William (Bill) C. McElroy Jr. working for Dohrman Instrument Company in Santa Clara, California . Up until this unit, most chart recorders were rack mounted and had one speed and one sensitivity range. McElroy's design

1209-479: The time of recording to the time that the film can be viewed. After the digital processing had been used, the archives of the seismograms were recorded on magnetic tapes. The data from the magnetic tapes can then be read back to reconstruct the original waveforms. Due to the deterioration of older magnetic tape medias, large number of waveforms from the archives in the early digital recording days are not recoverable. Today, many other forms are used to digitally record

World-Wide Standardized Seismograph Network - Misplaced Pages Continue

1248-409: The typical pen recorders of the day). The original models used a small mirror attached to a galvanometer to aim a high-intensity beam of light at photosensitive paper. The combination of the mirror's tiny mass combined with a chart drive that could move the paper up to 120 inches (3,000 mm) per second provided high bandwidth and impressive time axis resolution. Later models replaced the mirror with

1287-415: The writing medium, to make an impression, and then move while pressure is released. Where greater sensitivity and speed of response is required a mirror galvanometer , might be used instead, to deflected a beam of light which can be recorded photographically. Another type of paper chart recorder was the light beam oscillograph . It had a bandwidth of ~5 kHz full scale (approximately 100 times higher than

1326-458: Was a sensitive instrument that provided a permanent record of telegraph signals through long underwater telegraph cables. These recorders came to be referred to as pen registers , although this term later became part of law enforcement jargon referring to the use of such a register to record dialed telephone numbers. A patent for a 'Pressure Indicator and Recorder' was issued to William Henry Bristol , on September 18, 1888. Bristol went on to form

1365-518: Was an instant loading paper roll 'table-top' unit using an Integrated Chopper Circuit for signal conversion. The unit had plug in circuit boards, plug in single or multi-range modules and plug in single or multi-speed modules. The recorder's sensitivity was 1 microvolt to 100 volts full-scale, which at the time was an industry first. McElroy also aided in the design and build of the Gas Chromatograph used for analysing dirt and rock samples from

1404-529: Was built in the USSR with 168 stations using Kirnos seismographs. Seismogram A seismogram is a graph output by a seismograph . It is a record of the ground motion at a measuring station as a function of time. Seismograms typically record motions in three cartesian axes (x, y, and z), with the z axis perpendicular to the Earth's surface and the x- and y- axes parallel to the surface. The energy measured in

1443-514: Was issued a patent for this design in 1915. Chart recorders are still used in applications where instant visual feedback is required or where users do not have the need, opportunity or technical ability to download and view data on a computer or where no electrical power is available (such as in hazardous zones on an oil rig or in remote ecological studies). However, dataloggers' decreasing cost and power requirements allow them to increasingly replace chart recorders, even in situations where battery power

1482-502: Was not sufficiently developed to have that capability. The Eisenhower Administration therefore convened the Berkner panel to recommend ways to improve the nation's seismic detection abilities. The Berkner report, issued in 1959, was the basis of a comprehensive research and development program known as Project Vela Uniform, funded through the U.S. Department of Defense Defense Advanced Research Projects Agency (DARPA). DARPA then funded

1521-779: Was terminated in 1996. In the late 1970s digital recorders were added to 13 WWSSN stations; these "DWWSSN" stations operated as part of the Global Digital Seismographic Network (GSDN). Successor to the WWSSN is the Global Seismographic Network (GSN), operated by the Incorporated Research Institutions for Seismology , now EarthScope Consortium. A similar system, the Unified System of Seismic Stations (ESSN, transliterated from Russian),

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