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70-725: To the northwest of the rifts is the Siberian Craton , on the Eurasian Plate. The Sayan-Baikal and Mongolia-Okhotsk mobile belts are formations to the southeast of the rifts; beyond the Sayan-Baikal fold belt is the Amur Plate. Basins form along the rift. There are three basins in the area, the South Basin, Central Basin, and North Basin. In the North, half-grabens form smaller basins, such as

140-450: A seismogram . Such data is used to locate and characterize earthquakes , and to study the internal structure of Earth . A simple seismometer, sensitive to up-down motions of the Earth, is like a weight hanging from a spring, both suspended from a frame that moves along with any motion detected. The relative motion between the weight (called the mass) and the frame provides a measurement of

210-458: A feedback circuit. The amount of force necessary to achieve this is then recorded. In most designs the electronics holds a mass motionless relative to the frame. This device is called a "force balance accelerometer". It measures acceleration instead of velocity of ground movement. Basically, the distance between the mass and some part of the frame is measured very precisely, by a linear variable differential transformer . Some instruments use

280-408: A geo-sismometro , possibly the first use of a similar word to seismometer . Naturalist Nicolo Zupo devised an instrument to detect electrical disturbances and earthquakes at the same time (1784). The first moderately successful device for detecting the time of an earthquake was devised by Ascanio Filomarino in 1796, who improved upon Salsano's pendulum instrument, using a pencil to mark, and using

350-431: A linear variable differential capacitor . That measurement is then amplified by electronic amplifiers attached to parts of an electronic negative feedback loop . One of the amplified currents from the negative feedback loop drives a coil very like a loudspeaker . The result is that the mass stays nearly motionless. Most instruments measure directly the ground motion using the distance sensor. The voltage generated in

420-541: A copy of which can be found at the University Library in Bologna, and a further mercury seismoscope was constructed by Niccolò Cacciatore in 1818. James Lind also built a seismological tool of unknown design or efficacy (known as an earthquake machine) in the late 1790s. Pendulum devices were developing at the same time. Neapolitan naturalist Nicola Cirillo set up a network of pendulum earthquake detectors following

490-406: A digital seismograph can be simply input to a computer. It presents the data in a standard digital format (often "SE2" over Ethernet ). The modern broadband seismograph can record a very broad range of frequencies . It consists of a small "proof mass", confined by electrical forces, driven by sophisticated electronics . As the earth moves, the electronics attempt to hold the mass steady through

560-520: A given quake. Luigi Palmieri , influenced by Mallet's 1848 paper, invented a seismometer in 1856 that could record the time of an earthquake. This device used metallic pendulums which closed an electric circuit with vibration, which then powered an electromagnet to stop a clock. Palmieri seismometers were widely distributed and used for a long time. By 1872, a committee in the United Kingdom led by James Bryce expressed their dissatisfaction with

630-433: A hair attached to the mechanism to inhibit the motion of a clock's balance wheel. This meant that the clock would only start once an earthquake took place, allowing determination of the time of incidence. After an earthquake taking place on October 4, 1834, Luigi Pagani observed that the mercury seismoscope held at Bologna University had completely spilled over, and did not provide useful information. He therefore devised

700-414: A low-budget way to get some of the performance of the closed-loop wide-band geologic seismographs. Strain-beam accelerometers constructed as integrated circuits are too insensitive for geologic seismographs (2002), but are widely used in geophones. Some other sensitive designs measure the current generated by the flow of a non-corrosive ionic fluid through an electret sponge or a conductive fluid through

770-540: A portable device that used lead shot to detect the direction of an earthquake, where the lead fell into four bins arranged in a circle, to determine the quadrant of earthquake incidence. He completed the instrument in 1841. In response to a series of earthquakes near Comrie in Scotland in 1839, a committee was formed in the United Kingdom in order to produce better detection devices for earthquakes. The outcome of this

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840-482: A seismometer was deployed on the planet Mars by the InSight lander, the first time a seismometer was placed onto the surface of another planet. In Ancient Egypt , Amenhotep, son of Hapu invented a precursor of seismometer, a vertical wooden poles connected with wooden gutters on the central axis functioned to fill water into a vessel until full to detect earthquakes. In AD 132 , Zhang Heng of China's Han dynasty

910-508: A sense coil on the mass by the magnet directly measures the instantaneous velocity of the ground. The current to the drive coil provides a sensitive, accurate measurement of the force between the mass and frame, thus measuring directly the ground's acceleration (using f=ma where f=force, m=mass, a=acceleration). One of the continuing problems with sensitive vertical seismographs is the buoyancy of their masses. The uneven changes in pressure caused by wind blowing on an open window can easily change

980-499: A vacuum to reduce disturbances from air currents. Zollner described torsionally suspended horizontal pendulums as early as 1869, but developed them for gravimetry rather than seismometry. Early seismometers had an arrangement of levers on jeweled bearings, to scratch smoked glass or paper. Later, mirrors reflected a light beam to a direct-recording plate or roll of photographic paper. Briefly, some designs returned to mechanical movements to save money. In mid-twentieth-century systems,

1050-442: Is a stub . You can help Misplaced Pages by expanding it . Seismometer A seismometer is an instrument that responds to ground displacement and shaking such as caused by quakes , volcanic eruptions , and explosions . They are usually combined with a timing device and a recording device to form a seismograph . The output of such a device—formerly recorded on paper (see picture) or film, now recorded and processed digitally—is

1120-574: Is a digital strong-motion seismometer, or accelerograph . The data from such an instrument is essential to understand how an earthquake affects man-made structures, through earthquake engineering . The recordings of such instruments are crucial for the assessment of seismic hazard , through engineering seismology . A strong-motion seismometer measures acceleration. This can be mathematically integrated later to give velocity and position. Strong-motion seismometers are not as sensitive to ground motions as teleseismic instruments but they stay on scale during

1190-703: Is an ancient craton in the heart of Siberia . Today forming the Central Siberian Plateau , it formed an independent landmass prior to its fusion into Pangea during the Late Carboniferous - Permian . The Verkhoyansk Sea , a passive continental margin, was fringing the Siberian Craton to the east in what is now the East Siberian Lowland . Angaraland was named in the 1880s by Austrian geologist Eduard Suess who erroneously believed that in

1260-450: Is called seismometry , a branch of seismology . The concept of measuring the "shaking" of something means that the word "seismograph" might be used in a more general sense. For example, a monitoring station that tracks changes in electromagnetic noise affecting amateur radio waves presents an rf seismograph . And helioseismology studies the "quakes" on the Sun . The first seismometer

1330-450: Is made of shallow-water deposits and is often folded and faulted. Overlying this unit, separated by a small unconformity , is the 'middle rift' unit of Pliocene coarse grained sandstones and conglomerates . Finally there is the modern rift unit of fluvial, glacial, and deltaic sediments. Examining Pliocene and younger sediments reveals sands , argillites , and silts , indicating lacustrine deposition. The first seismic station in

1400-502: Is measured, it is usually the vertical because it is less noisy and gives better records of some seismic waves. The foundation of a seismic station is critical. A professional station is sometimes mounted on bedrock . The best mountings may be in deep boreholes, which avoid thermal effects, ground noise and tilting from weather and tides. Other instruments are often mounted in insulated enclosures on small buried piers of unreinforced concrete. Reinforcing rods and aggregates would distort

1470-443: Is placed under the arm, and a small sheet of metal mounted on the underside of the arm drags in the oil to damp oscillations. The level of oil, position on the arm, and angle and size of sheet is adjusted until the damping is "critical", that is, almost having oscillation. The hinge is very low friction, often torsion wires, so the only friction is the internal friction of the wire. Small seismographs with low proof masses are placed in

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1540-537: Is said to have invented the first seismoscope (by the definition above), which was called Houfeng Didong Yi (translated as, "instrument for measuring the seasonal winds and the movements of the Earth"). The description we have, from the History of the Later Han Dynasty , says that it was a large bronze vessel, about 2 meters in diameter; at eight points around the top were dragon's heads holding bronze balls. When there

1610-512: Is the output of the seismometer, which is recorded digitally. In other systems the weight is allowed to move, and its motion produces an electrical charge in a coil attached to the mass which voltage moves through the magnetic field of a magnet attached to the frame. This design is often used in a geophone , which is used in exploration for oil and gas. Seismic observatories usually have instruments measuring three axes: north-south (y-axis), east–west (x-axis), and vertical (z-axis). If only one axis

1680-511: Is thought to refer to a pendulum, though it is not known exactly how this was linked to a mechanism that would open only one dragon's mouth. The first earthquake recorded by this seismoscope was supposedly "somewhere in the east". Days later, a rider from the east reported this earthquake. By the 13th century, seismographic devices existed in the Maragheh observatory (founded 1259) in Persia, though it

1750-439: Is unclear whether these were constructed independently or based on the first seismoscope. French physicist and priest Jean de Hautefeuille described a seismoscope in 1703, which used a bowl filled with mercury which would spill into one of eight receivers equally spaced around the bowl, though there is no evidence that he actually constructed the device. A mercury seismoscope was constructed in 1784 or 1785 by Atanasio Cavalli ,

1820-924: The Cretaceous with Siberia remaining part of present-day northeastern Eurasia . Today, Siberia forms part of the landmass of Afro-Eurasia . To the east it is joined to the North American Plate at the Chersky Range . In around 250 million years from now Siberia may be in the subtropical region and part of the new supercontinent of Pangaea Proxima . [REDACTED] Africa [REDACTED] Antarctica [REDACTED] Asia [REDACTED] Australia [REDACTED] Europe [REDACTED] North America [REDACTED] South America [REDACTED] Afro-Eurasia [REDACTED] Americas [REDACTED] Eurasia [REDACTED] Oceania This palaeogeography article

1890-452: The Greek σεισμός, seismós , a shaking or quake, from the verb σείω, seíō , to shake; and μέτρον, métron , to measure, and was coined by David Milne-Home in 1841, to describe an instrument designed by Scottish physicist James David Forbes . Seismograph is another Greek term from seismós and γράφω, gráphō , to draw. It is often used to mean seismometer , though it is more applicable to

1960-785: The Paleozoic Era there were two large continents in the Northern Hemisphere: "Atlantis", which was North America connected to Europe via a peninsula (Greenland and Iceland), and "Angara-land", which would have been eastern Asia, named after the Angara River in Siberia. About 2.5 billion years ago (in the Siderian Period), Siberia was part of a continent called Arctica , along with the Canadian Shield . Around 1.1 billion years ago (in

2030-615: The Stenian Period), Siberia became part of the supercontinent of Rodinia , a state of affairs which lasted until the Tonian about 750 million years ago when it broke up, and Siberia became part of the landmass of Protolaurasia . During the Ediacaran Period around 600 million years ago, Protolaurasia became part of the southern supercontinent of Pannotia but around 550 million years ago, both Pannotia and Protolaurasia split up to become

2100-523: The grabens basalt volcanics erupted from either end of the rift system during the uplift. The grabens mostly spread without releasing magma, except the Tunkin Depression . Most basin deposits are from the late Oligocene , except in the north where basin deposits began in the Pliocene . Three series of sediment are present; the 'proto-rift', the 'middle rift', and the 'modern rift'. The proto-rift unit

2170-445: The inertia to stay still within the frame . The result is that the stylus scratched a pattern corresponding with the Earth's movement. This type of strong-motion seismometer recorded upon a smoked glass (glass with carbon soot ). While not sensitive enough to detect distant earthquakes, this instrument could indicate the direction of the pressure waves and thus help find the epicenter of a local quake. Such instruments were useful in

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2240-423: The 1731 Puglia Earthquake, where the amplitude was detected using a protractor to measure the swinging motion. Benedictine monk Andrea Bina further developed this concept in 1751, having the pendulum create trace marks in sand under the mechanism, providing both magnitude and direction of motion. Neapolitan clockmaker Domenico Salsano produced a similar pendulum which recorded using a paintbrush in 1783, labelling it

2310-630: The Baikal Rift Zone. Early volcanism has been confirmed to exist from the early Miocene , although it is believed that Oligocene Volcanism exists. The recognized volcanic centers are the Udokan Plateau , located about 400 km ENE of the northern tip of Lake Baikal, the Oka Plateau , located about 200 km WNW of the southwest tip of Lake Baikal, the Vitim Plateau, around 200 km east of

2380-644: The North Baikal Basin, and the Chara-Tokka Basin. The Central Basin is the deepest in the rift system. The largest fault it contains is the Morskiy Fault; however, another fault, the Primorsky is becoming the primary fault in the rift. The basins also display evidence of crustal thinning below the rift zone. The thickness of the crust beneath the rift is disputed, as the structures of the rift deep beneath

2450-482: The analysis of the 1906 San Francisco earthquake . Further analysis was performed in the 1980s, using these early recordings, enabling a more precise determination of the initial fault break location in Marin county and its subsequent progression, mostly to the south. Later, professional suites of instruments for the worldwide standard seismographic network had one set of instruments tuned to oscillate at fifteen seconds, and

2520-557: The continents of Laurentia , Baltica and Siberia. Siberia was an independent continent through the early Paleozoic until, during the Carboniferous Period, it collided with the minor continent of Kazakhstania . A subsequent collision with Euramerica/Laurussia during the Late Carboniferous - Permian formed Pangea . Pangaea split up during the Jurassic though Siberia stayed with Laurasia . Laurasia gradually split up during

2590-548: The current available seismometers, still using the large 1842 Forbes device located in Comrie Parish Church, and requested a seismometer which was compact, easy to install and easy to read. In 1875 they settled on a large example of the Mallet device, consisting of an array of cylindrical pins of various sizes installed at right angles to each other on a sand bed, where larger earthquakes would knock down larger pins. This device

2660-402: The density of the air in a room enough to cause a vertical seismograph to show spurious signals. Therefore, most professional seismographs are sealed in rigid gas-tight enclosures. For example, this is why a common Streckeisen model has a thick glass base that must be glued to its pier without bubbles in the glue. It might seem logical to make the heavy magnet serve as a mass, but that subjects

2730-451: The device to begin recording, and then a recording surface would produce a graphical illustration of the tremors automatically (a seismogram). However, the instrument was not sensitive enough, and the first seismogram produced by the instrument was in 1887, by which time John Milne had already demonstrated his design in Japan . In 1880, the first horizontal pendulum seismometer was developed by

2800-425: The first horizontal pendulum was used in a seismometer, reported by Milne (though it is unclear if he was the original inventor). After these inventions, Robert Mallet published an 1848 paper where he suggested ideas for seismometer design, suggesting that such a device would need to register time, record amplitudes horizontally and vertically, and ascertain direction. His suggested design was funded, and construction

2870-414: The first modern seismometer. This produced the first effective measurement of horizontal motion. Gray would produce the first reliable method for recording vertical motion, which produced the first effective 3-axis recordings. An early special-purpose seismometer consisted of a large, stationary pendulum , with a stylus on the bottom. As the earth started to move, the heavy mass of the pendulum had

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2940-450: The garden-gate described above. Vertical instruments use some kind of constant-force suspension, such as the LaCoste suspension. The LaCoste suspension uses a zero-length spring to provide a long period (high sensitivity). Some modern instruments use a "triaxial" or "Galperin" design , in which three identical motion sensors are set at the same angle to the vertical but 120 degrees apart on

3010-634: The horizontal. Vertical and horizontal motions can be computed from the outputs of the three sensors. Seismometers unavoidably introduce some distortion into the signals they measure, but professionally designed systems have carefully characterized frequency transforms. Modern sensitivities come in three broad ranges: geophones , 50 to 750 V /m; local geologic seismographs, about 1,500 V/m; and teleseismographs, used for world survey, about 20,000 V/m. Instruments come in three main varieties: short period, long period and broadband. The short and long period measure velocity and are very sensitive, however they 'clip'

3080-498: The light was reflected to a pair of differential electronic photosensors called a photomultiplier. The voltage generated in the photomultiplier was used to drive galvanometers which had a small mirror mounted on the axis. The moving reflected light beam would strike the surface of the turning drum, which was covered with photo-sensitive paper. The expense of developing photo-sensitive paper caused many seismic observatories to switch to ink or thermal-sensitive paper. After World War II,

3150-411: The lower crust is intruded by mafic sills . They interpret the extension as a pure shear process. Volcanism is generally associated with the rift. Hot springs are present both on land and under Lake Baikal, although thus far, no evidence of actual volcanism has been found in the immediate vicinity of the lake. Despite this, Cenozoic volcanism has occurred nearby and is probably associated with

3220-476: The next year, one being a common-pendulum seismometer and the other being the first seismometer using a damped horizontal pendulum. The innovative recording system allowed for a continuous record, the first to do so. The first seismogram was recorded on 3 November 1880 on both of Ewing's instruments. Modern seismometers would eventually descend from these designs. Milne has been referred to as the 'Father of modern seismology' and his seismograph design has been called

3290-417: The north by looking at offsets of morphological features, although this estimate does not agree with current models . The total throw that has occurred has been estimated at 7 ± 0.5 kilometres (4.35 ± 0.31 mi) in extension and 12 ± 1 kilometre (7.46 ± 0.62 mi) in the vertical direction. Due to the distance from active plate boundaries , the driving forces of

3360-417: The older instruments in which the measuring and recording of ground motion were combined, than to modern systems, in which these functions are separated. Both types provide a continuous record of ground motion; this record distinguishes them from seismoscopes , which merely indicate that motion has occurred, perhaps with some simple measure of how large it was. The technical discipline concerning such devices

3430-407: The other at ninety seconds, each set measuring in three directions. Amateurs or observatories with limited means tuned their smaller, less sensitive instruments to ten seconds. The basic damped horizontal pendulum seismometer swings like the gate of a fence. A heavy weight is mounted on the point of a long (from 10 cm to several meters) triangle, hinged at its vertical edge. As the ground moves,

3500-442: The pier as the temperature changes. A site is always surveyed for ground noise with a temporary installation before pouring the pier and laying conduit. Originally, European seismographs were placed in a particular area after a destructive earthquake. Today, they are spread to provide appropriate coverage (in the case of weak-motion seismology ) or concentrated in high-risk regions ( strong-motion seismology ). The word derives from

3570-473: The region was opened in Irkutsk in 1901, which began instrumental observations. New instruments were put in place in 1912, and the system was expanded in the 1950s and 1960s. The monitoring network is still in operation, although the minimum spacing has been criticized for exceeding 100 kilometres (62 mi) in the minimum distance between stations. Studies from foreign experiments also provide new information about

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3640-600: The rift are unknown; however, possibilities include the subduction of the Pacific Plate and the collision of the Indian subcontinent with Eurasia. Locally, there may be a mantle up-welling driving the extension. This latter theory is held by most Russian scientists. 53°30′N 108°00′E  /  53.5°N 108.0°E  / 53.5; 108.0 Siberia (continent) Siberia , also known as Siberian Craton , Angaraland (or simply Angara ) and Angarida ,

3710-536: The rift system. Along the boundary both normal and shear strains have occurred in the rift. Plates are diverging along the boundary at 3 to 4 millimetres (0.12 to 0.16 in) per year, although this varies along the system. In addition to divergent movement, left lateral strike-slip movement also occurs in the fault system, such as along the Sayan Fault. The rate of slip has been estimated at 3.2 ± 0.5 millimetres (0.126 ± 0.020 in) per year in

3780-507: The rift, and the Azas Plateau . The area was originally characterized by Precambrian and Paleozoic northeast-southwest fold and thrust belts . The Primorsky fault zone of the central basin was present at this time also. Volcanism began in the late Cretaceous in limited areas, but is mostly limited to the Miocene . The late Cretaceous is also the age of sedimentary rocks in some basins, and

3850-675: The same series lasted into the Eocene . Rifting resumed beginning in the Oligocene , and is commonly held to have increased since the middle Pliocene , causing the formation of basins in the form of grabens. The new rift structure may follow the Precambrian and Paleozoic faults, such as when the dormant Primorsky fault, of the Central Basin, began to extend again in the late Cenozoic . Magmatic activity and rifting may also be independent events. Outside of

3920-400: The seismograph to errors when the Earth's magnetic field moves. This is also why seismograph's moving parts are constructed from a material that interacts minimally with magnetic fields. A seismograph is also sensitive to changes in temperature so many instruments are constructed from low expansion materials such as nonmagnetic invar . The hinges on a seismograph are usually patented, and by

3990-475: The seismometers developed by Milne, Ewing and Gray were adapted into the widely used Press-Ewing seismometer . Modern instruments use electronic sensors, amplifiers, and recording devices. Most are broadband covering a wide range of frequencies. Some seismometers can measure motions with frequencies from 500 Hz to 0.00118 Hz (1/500 = 0.002 seconds per cycle, to 1/0.00118 = 850 seconds per cycle). The mechanical suspension for horizontal instruments remains

4060-413: The signal or go off-scale for ground motion that is strong enough to be felt by people. A 24-bit analog-to-digital conversion channel is commonplace. Practical devices are linear to roughly one part per million. Delivered seismometers come with two styles of output: analog and digital. Analog seismographs require analog recording equipment, possibly including an analog-to-digital converter. The output of

4130-438: The small motions involved, recording on soot-covered paper or photographic paper. Modern instruments use electronics. In some systems, the mass is held nearly motionless relative to the frame by an electronic negative feedback loop . The motion of the mass relative to the frame is measured, and the feedback loop applies a magnetic or electrostatic force to keep the mass nearly motionless. The voltage needed to produce this force

4200-435: The strongest seismic shaking. Strong motion sensors are used for intensity meter applications. Accelerographs and geophones are often heavy cylindrical magnets with a spring-mounted coil inside. As the case moves, the coil tends to stay stationary, so the magnetic field cuts the wires, inducing current in the output wires. They receive frequencies from several hundred hertz down to 1 Hz. Some have electronic damping,

4270-456: The surface are unknown. The difference in thickness of the crust, between the crust under the rift and that under the surrounding areas, has been bounded to be less than 10 kilometres (6.2 mi). Although some seismic data is evidence for a rise in the Lithosphere - Asthenosphere boundary, other researchers have claimed that there are deep structures which influence seismic activity, and that

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4340-643: The team of John Milne , James Alfred Ewing and Thomas Gray , who worked as foreign-government advisors in Japan, from 1880 to 1895. Milne, Ewing and Gray, all having been hired by the Meiji Government in the previous five years to assist Japan's modernization efforts, founded the Seismological Society of Japan in response to an Earthquake that took place on February 22, 1880, at Yokohama (Yokohama earthquake). Two instruments were constructed by Ewing over

4410-455: The time the patent has expired, the design has been improved. The most successful public domain designs use thin foil hinges in a clamp. Another issue is that the transfer function of a seismograph must be accurately characterized, so that its frequency response is known. This is often the crucial difference between professional and amateur instruments. Most are characterized on a variable frequency shaking table. Another type of seismometer

4480-442: The vertical ground motion . A rotating drum is attached to the frame and a pen is attached to the weight, thus recording any ground motion in a seismogram . Any movement from the ground moves the frame. The mass tends not to move because of its inertia , and by measuring the movement between the frame and the mass, the motion of the ground can be determined. Early seismometers used optical levers or mechanical linkages to amplify

4550-516: The weight stays unmoving, swinging the "gate" on the hinge. The advantage of a horizontal pendulum is that it achieves very low frequencies of oscillation in a compact instrument. The "gate" is slightly tilted, so the weight tends to slowly return to a central position. The pendulum is adjusted (before the damping is installed) to oscillate once per three seconds, or once per thirty seconds. The general-purpose instruments of small stations or amateurs usually oscillate once per ten seconds. A pan of oil

4620-539: Was an earthquake, one of the dragons' mouths would open and drop its ball into a bronze toad at the base, making a sound and supposedly showing the direction of the earthquake. On at least one occasion, probably at the time of a large earthquake in Gansu in AD 143, the seismoscope indicated an earthquake even though one was not felt. The available text says that inside the vessel was a central column that could move along eight tracks; this

4690-420: Was an inverted pendulum seismometer constructed by James David Forbes , first presented in a report by David Milne-Home in 1842, which recorded the measurements of seismic activity through the use of a pencil placed on paper above the pendulum. The designs provided did not prove effective, according to Milne's reports. It was Milne who coined the word seismometer in 1841, to describe this instrument. In 1843,

4760-520: Was attempted, but his final design did not fulfill his expectations and suffered from the same problems as the Forbes design, being inaccurate and not self-recording. Karl Kreil constructed a seismometer in Prague between 1848 and 1850, which used a point-suspended rigid cylindrical pendulum covered in paper, drawn upon by a fixed pencil. The cylinder was rotated every 24 hours, providing an approximate time for

4830-423: Was constructed in 'Earthquake House' near Comrie, which can be considered the world's first purpose-built seismological observatory. As of 2013, no earthquake has been large enough to cause any of the cylinders to fall in either the original device or replicas. The first seismographs were invented in the 1870s and 1880s. The first seismograph was produced by Filippo Cecchi in around 1875. A seismoscope would trigger

4900-653: Was made in China during the 2nd century. It was invented by Zhang Heng , a Chinese mathematician and astronomer. The first Western description of the device comes from the French physicist and priest Jean de Hautefeuille in 1703. The modern seismometer was developed in the 19th century. Seismometers were placed on the Moon starting in 1969 as part of the Apollo Lunar Surface Experiments Package . In December 2018,

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