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Passive Seismic
Passive seismic is the detection of natural low frequency earth movements, usually with the purpose of discerning geological structure and locate underground oil, gas, or other resources. Usually the data listening is done in multiple measurement points that are separated by several hundred meters, over periods of several hours to several days, using portable seismometers. The conclusions about the geological structure are based on the spectral analysis or on the mathematical reconstruction of the propagation and possible sources of the observed seismic waves. If the latter is planned, data are usually acquired in multiple (in the ideal case - all) points simultaneously, using so called synchronized lines. Reliability of the time reverse modelling can be further increased using results of reflection seismology about the distribution of the sound speed in the underground volume. Passive seismic usually focuses on a low frequency signals (0 to 10 Hz) and is sometimes called the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Seismometer Kum Hg
A seismometer is an instrument that responds to ground noises and shaking such as caused by earthquakes, Types of volcanic eruptions, 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 a seismogram. Such data is used to locate and characterize earthquakes, and to study the Earth's internal structure. Basic principles 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 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 fr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Seismometer
A seismometer is an instrument that responds to ground noises and shaking such as caused by earthquakes, 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 a seismogram. Such data is used to locate and characterize earthquakes, and to study the Earth's internal structure. Basic principles 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 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Seismic Wave
A seismic wave is a wave of acoustic energy that travels through the Earth. It can result from an earthquake, volcanic eruption, magma movement, a large landslide, and a large man-made explosion that produces low-frequency acoustic energy. Seismic waves are studied by seismologists, who record the waves using seismometers, hydrophones (in water), or accelerometers. Seismic waves are distinguished from seismic noise (ambient vibration), which is persistent low-amplitude vibration arising from a variety of natural and anthropogenic sources. The propagation velocity of a seismic wave depends on density and elasticity of the medium as well as the type of wave. Velocity tends to increase with depth through Earth's crust and mantle, but drops sharply going from the mantle to Earth's outer core. Earthquakes create distinct types of waves with different velocities. When recorded by a seismic observatory, their different travel times help scientists locate the quake's hypocen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reflection Seismology
Reflection seismology (or seismic reflection) is a method of exploration geophysics that uses the principles of seismology to estimate the properties of the Earth's subsurface from reflected seismic waves. The method requires a controlled seismic source of energy, such as dynamite or Tovex blast, a specialized air gun or a seismic vibrator. Reflection seismology is similar to sonar and echolocation. This article is about surface seismic surveys; for vertical seismic profiles, see VSP. History Reflections and refractions of seismic waves at geologic interfaces within the Earth were first observed on recordings of earthquake-generated seismic waves. The basic model of the Earth's deep interior is based on observations of earthquake-generated seismic waves transmitted through the Earth's interior (e.g., Mohorovičić, 1910). The use of human-generated seismic waves to map in detail the geology of the upper few kilometers of the Earth's crust followed shortly thereafter and h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Infrasonic Passive Differential Spectroscopy
Infrasonic passive seismic spectroscopy (IPSS) is a passive seismic low frequency technique used for mapping potential oil and gas hydrocarbon accumulations. It is part of the geophysical techniques also known under the generic naming passive seismic which includes also passive seismic tomography and micro seismic monitoring for petroleum, gas, and geothermal applications. In a larger scale, passive seismic includes the Global Seismic Network (GSN) earthquake monitoring. Regarding petroleum and geothermal exploration (within a small scale), the effect of fluid distribution on P-wave propagation in partially saturated rocks is responsible for the low frequency reservoir-related wavefield absorption. The high level of attenuation within the infrasonic bandwidth (below 10 Hz) of the seismic field observed in natural oil-saturated porous media during the last years (explained by mesoscopic homogeneous models) is the main responsible of the passive seismic wave field shifting w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geophone
A geophone is a device that converts ground movement (velocity) into voltage, which may be recorded at a recording station. The deviation of this measured voltage from the base line is called the seismic response and is analyzed for structure of the earth. Etymology The term geophone derives from the Greek word "γῆ (ge) " meaning "earth" and "phone" meaning "sound". Construction Geophones have historically been passive analog devices and typically comprise a spring-mounted wire coil moving within the field of a case-mounted permanent magnet to generate an electrical signal. Recent designs have been based on microelectromechanical systems (MEMS) technology which generates an electrical response to ground motion through an active feedback circuit to maintain the position of a small piece of silicon. The response of a coil/magnet geophone is proportional to ground velocity, while MEMS devices usually respond proportional to acceleration. MEMS have a much higher noise level (5 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
The Times Of Israel
''The Times of Israel'' is an Israeli multi-language online newspaper that was launched in 2012. It was co-founded by Israeli journalist David Horovitz, who is also the founding editor, and American billionaire investor Seth Klarman.Forbes: The World's Billionaires: Seth Klarman April 2014 Based in , it "documents developments in Israel, the Middle East and around the ." Along with its original English site, ''The Times of Israel'' publishes in |
Time Zone
A time zone is an area which observes a uniform standard time for legal, Commerce, commercial and social purposes. Time zones tend to follow the boundaries between Country, countries and their Administrative division, subdivisions instead of strictly following longitude, because it is convenient for areas in frequent communication to keep the same time. All time zones are defined as offsets from Coordinated Universal Time (UTC), ranging from UTC−12:00 to UTC+14:00. The UTC offset, offsets are usually a whole number of hours, but a few zones are offset by an additional 30 or 45 minutes, such as in Indian Standard Time, India, Time in Australia, South Australia and Nepal Time, Nepal. Some areas of higher latitude use daylight saving time for about half of the year, typically by adding one hour to local time during spring (season), spring and summer. List of UTC offsets In the table below, the locations that use daylight saving time (DST) are listed in their UTC offse ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Earthquake
An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, from those that are so weak that they cannot be felt, to those violent enough to propel objects and people into the air, damage critical infrastructure, and wreak destruction across entire cities. The seismic activity of an area is the frequency, type, and size of earthquakes experienced over a particular time period. The seismicity at a particular location in the Earth is the average rate of seismic energy release per unit volume. The word ''tremor'' is also used for Episodic tremor and slip, non-earthquake seismic rumbling. At the Earth's surface, earthquakes manifest themselves by shaking and displacing or disrupting the ground. When the epicenter of a large earthquake is located offshore, the seabed may be displaced sufficiently to cause ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Apollo Lunar Surface Experiments Package
The Apollo Lunar Surface Experiments Package (ALSEP) comprised a set of scientific instruments placed by the astronauts at the landing site of each of the five Apollo missions to land on the Moon following Apollo 11 (Apollos 12, 14, 15, 16, and 17). Apollo 11 left a smaller package called the Early Apollo Scientific Experiments Package, or EASEP. Background The instrumentation and experiments that would comprise ALSEP were decided in February 1966. Specifically, the experiments, institutions responsible, and principal investigators and coinvestigators were: * Passive Lunar Seismic Experiment: Massachusetts Institute of Technology, Frank Press; Columbia University, George Sutton; Georgia Tech, Robert Hostetler * Lunar Tri-axis Magnetometer: Ames Research Center, C. P. Sonett; Marshall Space Flight Center, Jerry Modisette. * Medium-Energy Solar Wind: Jet Propulsion Laboratory, C. W. Snyder and M. M. Neugebauer. * Suprathermal Ion Detection: Rice University, J. W. Freeman, Jr. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reflection Seismology
Reflection seismology (or seismic reflection) is a method of exploration geophysics that uses the principles of seismology to estimate the properties of the Earth's subsurface from reflected seismic waves. The method requires a controlled seismic source of energy, such as dynamite or Tovex blast, a specialized air gun or a seismic vibrator. Reflection seismology is similar to sonar and echolocation. This article is about surface seismic surveys; for vertical seismic profiles, see VSP. History Reflections and refractions of seismic waves at geologic interfaces within the Earth were first observed on recordings of earthquake-generated seismic waves. The basic model of the Earth's deep interior is based on observations of earthquake-generated seismic waves transmitted through the Earth's interior (e.g., Mohorovičić, 1910). The use of human-generated seismic waves to map in detail the geology of the upper few kilometers of the Earth's crust followed shortly thereafter and h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
