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A seismometer is the internal part of the seismograph, which may be a pendulum or a mass mounted on a spring; however, it is often used synonymously with "seismograph".
Seismographs are instruments used to record the motion of the ground during an earthquake. They are installed in the ground throughout the world and operated as part of a seismographic network. The earliest "seismoscope" was invented by the Chinese philosopher Chang Heng in A.D. 132. This did not, however, record earthquakes; it only indicated that an earthquake was occurring. The first seismograph was developed in 1890.
A seismograph is securely mounted onto the surface of the earth so that when the earth shakes, the entire unit shakes with it EXCEPT for the mass on the spring, which has inertia and remains in the same place. As the seismograph shakes under the mass, the recording device on the mass records the relative motion between itself and the rest of the instrument, thus recording the ground motion. In reality, these mechanisms are no longer manual, but instead work by measuring electronic changes produced by the motion of the ground with respect to the mass.
A seismogram is the recording of the ground shaking at the specific location of the instrument. On a seismogram, the HORIZONTAL axis = time (measured in seconds) and the VERTICAL axis= ground displacement (usually measured in millimeters). When there is NO EARTHQUAKE reading, there is just a straight line except for small wiggles caused by local disturbance or "noise" and the time markers. Seismograms are digital now - there are no more paper recordings.
Learn More: Glossary of earthquake terms
Earthquakes are recorded by a seismographic network. Each seismic station in the network measures the movement of the ground at that site. The slip of one block of rock over another in an earthquake releases energy that makes the ground vibrate. That vibration pushes the adjoining piece of ground and causes it to vibrate, and thus the energy travels out from the earthquake hypocenter in a wave...
Earthquake size, as measured by the Richter Scale is a well known, but not well understood, concept. The idea of a logarithmic earthquake magnitude scale was first developed by Charles Richter in the 1930's for measuring the size of earthquakes occurring in southern California using relatively high-frequency data from nearby seismograph stations. This magnitude scale was referred to as ML, with...
Magnitude scales, like the moment magnitude, measure the size of the earthquake at its source. An earthquake has one magnitude. The magnitude does not depend on where the measurement is made. Often, several slightly different magnitudes are reported for an earthquake. This happens because the relation between the seismic measurements and the magnitude is complex and different procedures will often...
For earthquakes that occurred between about 1890 (when modern seismographs came into use) and 1935 when Charles Richter developed the magnitude scale, people went back to the old records and compared the seismograms from those days with similar records for later earthquakes. For earthquakes prior to about 1890, magnitudes have been estimated by looking at the physical effects (such as amount of...
When an earthquake occurs, one of the first questions is "where was it?" The location may tell us what fault it was on and where damage (if any) most likely occurred. Unfortunately, Earth is not transparent and we can't just see or photograph the earthquake disturbance like meteorologists can photograph clouds. When an earthquake occurs, it generates an expanding wavefront from the earthquake...
The duration of an earthquake is related to its magnitude but not in a perfectly strict sense. There are two ways to think about the duration of an earthquake. The first is the length of time it takes for the fault to rupture and the second is the length of time shaking is felt at any given point (e.g. when someone says "I felt it shake for 10 seconds" they are making a statement about the...
Magnitude calculations are based on a logarithmic scale, so a ten-fold drop in amplitude decreases the magnitude by 1. If an amplitude of 20 millimetres as measured on a seismic signal corresponds to a magnitude 2 earthquake, then: 10 times less (2 millimetres) corresponds to a magnitude of 1; 100 times less (0.2 millimetres) corresponds to magnitude 0; 1000 times less (0.02 millimetres)...
An earthquake cannot physically occur at a depth of 0 km or -1km (above the surface of the earth). In order for an earthquake to occur, two blocks of crust must slip past one another, and it is impossible for this to happen at or above the surface of the earth. So why do we report that the earthquake occurred at a depth of 0 km or event as a negative depth sometimes? First of all, the depth of an...
It is relatively easy to acquire the necessary materials and build your own seismometer. The links here are to various sources with information on how to build a seismometer. They range from very simple and inexpensive to sophisticated and pricey. Model Seismograph - Classroom Demonstration Build your own Seismograph Station Build Your Own Seismograph Amateur Seismology Homebuilt Seismograph FAQ
The earliest seismoscope was invented by the Chinese philosopher Chang Heng in A.D. 132. This was a large urn on the outside of which were eight dragon heads facing the eight principal directions of the compass. Below each dragon head was a toad with its mouth opened toward the dragon. When an earthquake occurred, one or more of the eight dragon-mouths would release a ball into the open mouth of...
A geoid is the irregular-shaped “ball” that scientists use to more accurately calculate depths of earthquakes, or any other deep object beneath the earth’s surface. Currently, we use the “WGS84” version (World Geodetic System of 1984). If Earth were a perfect sphere, calculations of depth and distances would be easy because we know the equations for those calculations on a sphere. However, the...
On June 6, USGS Hawaiian Volcano Observatory field engineers installed a new seismometer on the Southwest Rift Zone of Kīlauea to monitor earthquakes. The new seismic station is co-located at an existing monitoring station consisting of a GPS and high-resolution gas monitoring equipment.
On June 6, USGS Hawaiian Volcano Observatory field engineers installed a new seismometer on the Southwest Rift Zone of Kīlauea to monitor earthquakes. The new seismic station is co-located at an existing monitoring station consisting of a GPS and high-resolution gas monitoring equipment.
USGS scientists Nicholas van der Elst and Alan Yong installing a seismometer near the 2019 Ridgecrest earthquakes in southern California in order to record its aftershocks.
USGS scientists Nicholas van der Elst and Alan Yong installing a seismometer near the 2019 Ridgecrest earthquakes in southern California in order to record its aftershocks.
Webicorder record from the 24-hours at the MEM seismometer station in Long Valle
Webicorder record from the 24-hours at the MEM seismometer station in Long Valle
Seismometers (instruments for recording earthquakes) are tested and fitted at the USGS Cascades Volcano Observatory before going out into the field.
Seismometers (instruments for recording earthquakes) are tested and fitted at the USGS Cascades Volcano Observatory before going out into the field.
This video provides a tutorial for anyone interested in interpreting the seismic records on public webicorder displays.
This video provides a tutorial for anyone interested in interpreting the seismic records on public webicorder displays.
Seismogram signal examples from volcanic earthquakes: volcano tectonic (VT) Low Frequency (LF)/Deep Long-Period (DLP), hybrid (mix of VT and LF), very low frequency (VLF), and Tremor.
Seismogram signal examples from volcanic earthquakes: volcano tectonic (VT) Low Frequency (LF)/Deep Long-Period (DLP), hybrid (mix of VT and LF), very low frequency (VLF), and Tremor.
Seismologists demonstrates how an earthquake's S and P waves travel through the earth at a CVO public open house.
Seismologists demonstrates how an earthquake's S and P waves travel through the earth at a CVO public open house.
USGS seimologist Doug Given works with colleagues from the Bureau des Mines et de l'Energie to install a seismometer. Seismometers monitor the earth's movement and can detect and measure aftershocks. Given traveled to Haiti with USGS colleagues Susan Hough, Mark Meremonte, and J. Zebulon Maharrey shortly after a magnitude-7 earthquake struck on Jan. 12, 2010.
USGS seimologist Doug Given works with colleagues from the Bureau des Mines et de l'Energie to install a seismometer. Seismometers monitor the earth's movement and can detect and measure aftershocks. Given traveled to Haiti with USGS colleagues Susan Hough, Mark Meremonte, and J. Zebulon Maharrey shortly after a magnitude-7 earthquake struck on Jan. 12, 2010.
Earthquakes are recorded by a seismographic network. Each seismic station in the network measures the movement of the ground at that site. The slip of one block of rock over another in an earthquake releases energy that makes the ground vibrate. That vibration pushes the adjoining piece of ground and causes it to vibrate, and thus the energy travels out from the earthquake hypocenter in a wave...
Earthquake size, as measured by the Richter Scale is a well known, but not well understood, concept. The idea of a logarithmic earthquake magnitude scale was first developed by Charles Richter in the 1930's for measuring the size of earthquakes occurring in southern California using relatively high-frequency data from nearby seismograph stations. This magnitude scale was referred to as ML, with...
Magnitude scales, like the moment magnitude, measure the size of the earthquake at its source. An earthquake has one magnitude. The magnitude does not depend on where the measurement is made. Often, several slightly different magnitudes are reported for an earthquake. This happens because the relation between the seismic measurements and the magnitude is complex and different procedures will often...
For earthquakes that occurred between about 1890 (when modern seismographs came into use) and 1935 when Charles Richter developed the magnitude scale, people went back to the old records and compared the seismograms from those days with similar records for later earthquakes. For earthquakes prior to about 1890, magnitudes have been estimated by looking at the physical effects (such as amount of...
When an earthquake occurs, one of the first questions is "where was it?" The location may tell us what fault it was on and where damage (if any) most likely occurred. Unfortunately, Earth is not transparent and we can't just see or photograph the earthquake disturbance like meteorologists can photograph clouds. When an earthquake occurs, it generates an expanding wavefront from the earthquake...
The duration of an earthquake is related to its magnitude but not in a perfectly strict sense. There are two ways to think about the duration of an earthquake. The first is the length of time it takes for the fault to rupture and the second is the length of time shaking is felt at any given point (e.g. when someone says "I felt it shake for 10 seconds" they are making a statement about the...
Magnitude calculations are based on a logarithmic scale, so a ten-fold drop in amplitude decreases the magnitude by 1. If an amplitude of 20 millimetres as measured on a seismic signal corresponds to a magnitude 2 earthquake, then: 10 times less (2 millimetres) corresponds to a magnitude of 1; 100 times less (0.2 millimetres) corresponds to magnitude 0; 1000 times less (0.02 millimetres)...
An earthquake cannot physically occur at a depth of 0 km or -1km (above the surface of the earth). In order for an earthquake to occur, two blocks of crust must slip past one another, and it is impossible for this to happen at or above the surface of the earth. So why do we report that the earthquake occurred at a depth of 0 km or event as a negative depth sometimes? First of all, the depth of an...
It is relatively easy to acquire the necessary materials and build your own seismometer. The links here are to various sources with information on how to build a seismometer. They range from very simple and inexpensive to sophisticated and pricey. Model Seismograph - Classroom Demonstration Build your own Seismograph Station Build Your Own Seismograph Amateur Seismology Homebuilt Seismograph FAQ
The earliest seismoscope was invented by the Chinese philosopher Chang Heng in A.D. 132. This was a large urn on the outside of which were eight dragon heads facing the eight principal directions of the compass. Below each dragon head was a toad with its mouth opened toward the dragon. When an earthquake occurred, one or more of the eight dragon-mouths would release a ball into the open mouth of...
A geoid is the irregular-shaped “ball” that scientists use to more accurately calculate depths of earthquakes, or any other deep object beneath the earth’s surface. Currently, we use the “WGS84” version (World Geodetic System of 1984). If Earth were a perfect sphere, calculations of depth and distances would be easy because we know the equations for those calculations on a sphere. However, the...
On June 6, USGS Hawaiian Volcano Observatory field engineers installed a new seismometer on the Southwest Rift Zone of Kīlauea to monitor earthquakes. The new seismic station is co-located at an existing monitoring station consisting of a GPS and high-resolution gas monitoring equipment.
On June 6, USGS Hawaiian Volcano Observatory field engineers installed a new seismometer on the Southwest Rift Zone of Kīlauea to monitor earthquakes. The new seismic station is co-located at an existing monitoring station consisting of a GPS and high-resolution gas monitoring equipment.
USGS scientists Nicholas van der Elst and Alan Yong installing a seismometer near the 2019 Ridgecrest earthquakes in southern California in order to record its aftershocks.
USGS scientists Nicholas van der Elst and Alan Yong installing a seismometer near the 2019 Ridgecrest earthquakes in southern California in order to record its aftershocks.
Webicorder record from the 24-hours at the MEM seismometer station in Long Valle
Webicorder record from the 24-hours at the MEM seismometer station in Long Valle
Seismometers (instruments for recording earthquakes) are tested and fitted at the USGS Cascades Volcano Observatory before going out into the field.
Seismometers (instruments for recording earthquakes) are tested and fitted at the USGS Cascades Volcano Observatory before going out into the field.
This video provides a tutorial for anyone interested in interpreting the seismic records on public webicorder displays.
This video provides a tutorial for anyone interested in interpreting the seismic records on public webicorder displays.
Seismogram signal examples from volcanic earthquakes: volcano tectonic (VT) Low Frequency (LF)/Deep Long-Period (DLP), hybrid (mix of VT and LF), very low frequency (VLF), and Tremor.
Seismogram signal examples from volcanic earthquakes: volcano tectonic (VT) Low Frequency (LF)/Deep Long-Period (DLP), hybrid (mix of VT and LF), very low frequency (VLF), and Tremor.
Seismologists demonstrates how an earthquake's S and P waves travel through the earth at a CVO public open house.
Seismologists demonstrates how an earthquake's S and P waves travel through the earth at a CVO public open house.
USGS seimologist Doug Given works with colleagues from the Bureau des Mines et de l'Energie to install a seismometer. Seismometers monitor the earth's movement and can detect and measure aftershocks. Given traveled to Haiti with USGS colleagues Susan Hough, Mark Meremonte, and J. Zebulon Maharrey shortly after a magnitude-7 earthquake struck on Jan. 12, 2010.
USGS seimologist Doug Given works with colleagues from the Bureau des Mines et de l'Energie to install a seismometer. Seismometers monitor the earth's movement and can detect and measure aftershocks. Given traveled to Haiti with USGS colleagues Susan Hough, Mark Meremonte, and J. Zebulon Maharrey shortly after a magnitude-7 earthquake struck on Jan. 12, 2010.