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Topic: Blind thrust earthquake

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In the News (Tue 23 Jul 19)

  Blind thrust earthquake - Wikipedia, the free encyclopedia
A blind thrust earthquake is an earthquake along a thrust fault that has not been mapped by standard surface geological mapping, hence the designation "blind".
Although such earthquakes are not amongst the most violent, they sometimes constitute the most deadly, as conditions combine to form a classic urban earthquake which greatly affects urban seismic risk.
Blind thrust faults generally exist near plate margins (plate tectonics), in the broad disturbance zone.
en.wikipedia.org /wiki/Blind_thrust_earthquake   (307 words)

Blind thrust earthquake A blind thrust earthquake is a particularly deadly type of urban seismic risk.
Earthquake An earthquake is a trembling or shaking movement of the intraplate earthquakes.
Earthquake (movie) Earthquake was the title of a disaster movies of the era that placed an all star cast in life and dea...
www.brainyencyclopedia.com /topics/earthquake.html   (398 words)

 Encyclopedia: Earthquake
Earthquakes also occur in volcanic regions and as the result of a number of anthropogenic sources, such as reservoir induced seismicity, mining and the removal or injection of fluids into the crust.
Earthquakes have also been known to be caused by the removal of natural gas from subsurface deposits, for instance in the northern Netherlands.
Earthquake insurance is a form of property insurance that pays the policyholder in the event of an earthquake that causes damage to the property.
www.nationmaster.com /encyclopedia/Earthquake   (5111 words)

 Intraplate earthquake - Wikipedia, the free encyclopedia
A series of famous intraplate earthquakes occurred on the New Madrid fault zone in 1812 that were above magnitude 8 and were felt for hundreds of miles.
The Charleston quake was particularly surprising because unlike Boston and New York the area had almost no history of even minor earthquakes (to put in perspective, in addition to the three northeastern U.S. events previously mentioned, a more moderate magnitude 4 earthquake was recorded just north of New York City in 1985).
An especially dangerous form of earthquake, which has been involved in many deaths is the blind thrust earthquake, although this is more associated with interplate earthquakes.
en.wikipedia.org /wiki/Intraplate_earthquake   (405 words)

 High Quality Earthquake Animations
Earthquakes on strike-slip faults produce strong shaking in the horizontal direction, whereas earthquakes on thrust faults produce strong shaking in both the horizontal and vertical directions.
Earthquake rupture on a blind thrust fault that has a dip angle of 23 degrees.
Earthquake rupture on a thrust fault that breaks the surface and has a dip angle of 23 degrees.
pasadena.wr.usgs.gov /office/baagaard/research/animations/animations.html   (547 words)

 BSSA, Volume 91:6   (Site not responding. Last check: 2007-09-10)
Mapping of the Reelfoot blind thrust using portable array for numerical data acquisition (PANDA) seismicity suggests that it is a complex fault that changes its geometry along strike.
The thrust appears to be bounded to the north by an east-trending strike-slip fault.
Although some segmentation of the blind thrust is observed from the mapping of 3-km-wide strips of seismicity oriented perpendicular to the fault, it does not appear to be significant enough to prevent rupture along its entire length.
www.seismosoc.org /publications/BSSA_html/bssa_91-6/00276.html   (297 words)

 Hidden fault may contribute to Bay Area earthquake risk
Hypothetical blind thrusts are schematically indicated by 'dashed' thrust fault symbols - are purely schematic at present.
Earthquakes are not unusual in the San Francisco Bay Area, but a team of Penn State geoscientists believes that the hazard may be greater than previously thought because of a hidden fault under Marin County.
Assuming there is a blind thrust fault, the slip rate on the fault would need to be 3 to 4 millimeters to even out the discrepancies north and south of the Golden Gate Bridge.
www.eurekalert.org /pub_releases/2004-12/ps-hfm120904.php   (944 words)

 earthquake   (Site not responding. Last check: 2007-09-10)
A trembling or shaking of the earth that is volcanic or tectonic (seismic) in origin, often resulting in severe damage.
An earthquake under the ocean or the sea is a "peril of the seas" under an ocean marine policy.
Earthquake coverage for personal property can be added by attaching endorsements to the dwelling policy (ISO form DP 04 69) or to the homeowners policy (ISO form HO 04 54).
insurance.cch.com /rupps/earthquake.htm   (69 words)

 Scientists Identify a Major Fault Under Los Angeles That Could Produce Quake
Thrust faults, which exist elsewhere and have long been thought to lie beneath Los Angeles, in part because of surface features found within the city, are so called because of the activity they induce in earthquakes.
The blind thrust faults of Los Angeles, Dr. Shaw explained, are caused by the relative motion of the North American and Pacific plates, two huge masses of crust that are sliding past each other along the San Andreas fault.
Shaw said, that led to the discovery of the newly identified fault, called the Puente Hills blind thrust because it lies along the Puente Hills near the town of Whittier, in Orange County.
partners.nytimes.com /library/national/science/030599sci-la-quake.html   (1040 words)

 [No title]   (Site not responding. Last check: 2007-09-10)
The source is implemented in the finite-difference grid by adding to where is the ij\125th component of the moment tensor for the earthquake, V\112=\112dx3 is the cell volume, and is the ij\125th component of the stress tensor on the fault at time t.
The amplification south and east of the basin for SAF is a result of predominantly southward propagating surface waves generated by the wavefield impinging onto the basin structure from the North.
The For the eight scenario earthquakes, the amplification tends to increase with distance from the causative fault to the basin structure.
www.crustal.ucsb.edu /~kbolsen/PhaseIII/aug5.txt   (3581 words)

 Thomas H. Heaton   (Site not responding. Last check: 2007-09-10)
That is, the number of earthquakes generally decreases by a factor of ten for each unit increase in magnitude, but the energy of an individual earthquake increases by a factor of 32.
If we assume that M 8.0 is the largest earthquake magnitude that an earthquake can have in California, then there is three times as much energy released in the M 7 to 8 earthquakes as there is in all other earthquakes smaller than M 7.
Therefore, it is of critical importance to understand the fundamental dynamics of earthquake rupture to understand the stress state of the crust.
www.gps.caltech.edu /faculty/heaton   (3161 words)

 Intraplate earthquake   (Site not responding. Last check: 2007-09-10)
Although the theory of plate tectonics well describes the mechanisms for interplate earthquakes (earthquakes at plate boundaries), there is the fact that very large intraplate earthquakes (earthquake within plates) can inflict heavy damage on towns and cities.
Historic examples of this occurred in Boston in 1755 (the largest U.S. earthquake ever recorded east of the New Madrid fault zone, some estimates put its magnitude as high as 7.0), New York City in 1737 and 1884 (both quakes estimated at about 5.5 magnitude) and Charleston, SC in 1886 (estimated magnitude 6.5).
An especially dangerous form of earthquake, which has been involved in many deaths is the blind thrust earthquake.
read-and-go.hopto.org /Seismology/Intraplate-earthquake.html   (408 words)

 Researchers Solve Indian Earthquake Mystery
Boulder, April 15, The mystery of what caused a great earthquake in northeast India in 1897 that killed several thousand people and reduced all masonry buildings to rubble in a region roughly the size of England finally appears to have been solved.
The blind-thrust Assam earthquake was similar to the earthquake that devastated Bhuj, India, at the opposite end of the continent on Jan. 26, killing an estimated 25,000 people, Bilham said.
Most scientists previously believed the Assam earthquake was caused by a rupture on a Himalayan thrust fault that dipped to the north and propagated south of Bhutan, a small kingdom between India and China.
www.gisdevelopment.net /news/2001/apr/na022.htm   (758 words)

 t61b in fm02
Fold scarps of the Chi-Chi earthquake appear in the Ailiao village (east of Tsaotun), Hsintse folded terrace, and western limb of the Tungshih antcilne.
Combination of the near-surface creeping and the subsurface repeated earthquakes provided insights on the mechanical behaviors of the Chihshang fault, which are likely related to the geological materials of the converging island-arc: week m‚lange in the near-surface fault zone and strong volcanic basement in the subsurface seismogenic zone.
In contrast, the rocks of the eastern domain record an early history within the w-vergent thrust belt that is overprinted by ductile left lateral shear and the contrasting kinematics of the east-facing wedge and the boundary with the Longitudinal Valley.
www.agu.org /cgi-bin/SFgate/SFgate?&listenv=table&multiple=1&range=1&directget=1&application=fm02&database=/data/epubs/wais/indexes/fm02/fm02&maxhits=200&="T61B"   (9995 words)

At its eastern end, the Oak Ridge thrust becomes progessively more difficult to trace, and appears to be overthrust by the Santa Susana fault, thus becoming a blind thrust fault.
Indeed, the fault associated with the 1994 Northridge earthquake is probably part of the Oak Ridge fault system, as it shares many of the characteristics of this fault.
This blind thrust fault is known either as the Pico Thrust, named for the Pico Anticline (a geologic fold it is creating), or as the Northridge Thrust, for more obvious reasons.
www.data.scec.org /fault_index/oakridge.html   (199 words)

 Caltech Press Release, 1/12/1995, James Dolan, Kerry Sieh, Susan Hough, Thomas Heaton, John Hall, Marvin Halling
The scientists conclude that both the likelihood of major earthquakes in the region and the potential for damage to certain types of large buildings are greater than was previously thought.
Her theoretical work is based not only on slip measurements, but also on a distribution pattern of earthquake sizes that is well established from decades of observations: for every magnitude 7 in a certain area and time period, there will also be roughly 10 magnitude 6s and 100 magnitude 5s.
Hough used earthquakes of magnitude 6.5 to 6.7 as a simplification in her study, and because millions of people are familiar with this size from the Northridge and Sylmar events.
pr.caltech.edu /media/Press_Releases/PR11607.html   (1671 words)

 Looking for a Blind Thrust Fault   (Site not responding. Last check: 2007-09-10)
After the earthquake, examination of surface faults around Northridge did not reveal that any offset had occurred.
Therefore, the fault that moved must be a blind thrust fault, and seismologists would need to analyze a variety of earthquake data to pinpoint its location.
To find the blind thrust fault responsible for the earthquake, geologists examined the location of the earthquake epicenter and aftershocks, ground shaking intensity maps, ground motion maps, and the depth to the earthquake’s focus.
www.classzone.com /books/earth_science/terc/content/investigations/es1010/es1010page03.cfm   (152 words)

 Northridge Earthquake
The earthquake occurred along a "blind" thrust fault, close to the San Andreas fault.
Note that a blind fault is a fault which does not extend to the surface.
The Northridge earthquake was the worst earthquake in the Los Angeles basin since the San Fernando earthquake in 1971, which had a 6.7 magnitude.
www.vibrationdata.com /earthquakes/northridge.htm   (336 words)

 Cornell Science News   (Site not responding. Last check: 2007-09-10)
The quake, a 6.6-Richter scale temblor that killed dozens and caused enough damage to make it the costliest quake in U.S. history, was a "thrust" type earthquake on a blind, or hidden, fault in which one part of the Earth's crust rides up another part of the crust.
A large earthquake in Alaska in 1964 that caused faulting along 800 kilometers and was about 9.0 in magnitude was such an event, Barazangi said.
Also, a 1,000-km long earthquake in Chile in 1960 was the largest magnitude earthquake ever recorded with instruments, at 9.4 on a scale that measures total energy release, not just surface wave intensity, like the Richter scale, Barazangi said.
www.news.cornell.edu /science/PRST94/PRST029406.html   (538 words)

 Characterization of Earthquake Ground Motion for Severity and Damage Potential
One of the most important decisions in carrying out proper design is to select a design earthquake that adequately represents the ground motion expected at a particular site and in particular the motion that would drive the structure to its critical response, resulting in the highest damage potential.
During the past 15 years an ever-increasing database of recorded earthquakes has indicated that the dynamic characteristics of the ground motion can vary significantly between recording stations that are located in the same general area.
For example, this was the case during the earthquake at Bucharest, Romania, in March 1977.
nisee.berkeley.edu /lessons/singh.html   (1934 words)

 The Great 1857 "Fort Tejon" Earthquake
And the largest earthquake to hit Southern California in historic times occurred on January 9th, 1857, and it came to be known as the great "Fort Tejon" earthquake, although such appellation could be very misleading.
Technically, Parkfield was the epicenter of this earthquake, as it was the origin of the rupture, but most scientists would be more concerned with the extent and location of the entire rupture; Fort Tejon was approximately the midway point of the rupture.
The earthquake actually acquired its name because Fort Tejon was the only populated locality near the fault, and naturally, the Fort suffered more damage than the rest of sparsely-populated 1857 Southern California.
www.cco.caltech.edu /~meltzner/tejon.html   (672 words)

 Researchers Solve Century-Old Earthquake Mystery In India
Virginia Earthquake Not A Fluke In The Seismically Active Southeast (December 12, 2003) -- At 3:59 p.m.
This moderate earthquake was the strongest seismic event to shake the area in 30 years,...
MIT Researchers Monitoring Earthquakes In Turkey Say Istanbul Could Be Next Target (August 19, 1999) -- This week's earthquake, which killed hundreds in northwestern Turkey, increased the likelihood of a future earthquake near the metropolis of Istanbul by increasing the forces on the fault just...
www.sciencedaily.com /releases/2001/04/010412081544.htm   (915 words)

 MARIN COUNTY / Sinister quake hazard may lurk beneath Mount Tam / Scientists believe 'blind' fault could induce 6.5 ...   (Site not responding. Last check: 2007-09-10)
If the hypothetical "blind thrust'' fault is real and ruptures in a quake, its proximity to densely populated areas in Marin and San Francisco -- especially the Marina district, which stands on soil that can liquefy in intense shaking -- means it could cause widespread damage.
Blind thrust faults are like sharks -- they strike from beneath, without warning.
In 1994, a previously unknown blind thrust fault stunned state seismologists when it caused the 6.7 magnitude Northridge quake.
www.sfgate.com /cgi-bin/article.cgi?f=/c/a/2004/12/16/BAGK4ACKAP1.DTL&type=sports   (871 words)

 Nat' Academies Press, Living on an Active Earth: Perspectives on Earthquake Science (2003)
T.H. Heaton, Evidence for and implications of self-healing pulses of slip in earthquake rupture, Phys.
Studies of moderate to large earthquakes in the far field using P- and S- wave pulse shapes often depict earthquake rupture with multiple point sources (H. Kanamori and G.S. Stewart, Seismological aspects of the Guatemala earthquake of February 4, 1976, J.
The pulse shape of far-field body waves can be used to infer the spatial and temporal distribution of slip on the fault; however, only in the case of particularly large earthquakes is it possible to resolve spatial and temporal variation of slip on the fault plane at teleseismic distances.
www.nap.edu /books/0309065623/html/339.html   (830 words)

 SGER Group - Harvard University. Research in Active Blind-Thrust Faults [Carlos Rivero]   (Site not responding. Last check: 2007-09-10)
The origin of this earthquake has been controversial due to the mismatch between its evident reverse motion derived from focal mechanism and its common association with the San Diego Trough Strike Slip Fault.
Note the precise correlation between the mapped surface of the Thirtymile thrust, and the cluster of relocated hypocenters.
Also note that the occurrence of the earthquake cannot be explain by activity on the San Diego Trough Fault, because this fault is restricted to the structural trough located in the hanging wall of the low-angle thrust.
structure.harvard.edu /~rivero/Quake.html   (182 words)

 [No title]   (Site not responding. Last check: 2007-09-10)
We propose that a small segment of this blind thrust caused the 1987 Whittier Narrows (M 6.0) earthquake, the origin of which has remained controversial due to the lack of a surface fault trace and uncertainties in earthquake locations.
The relocated aftershock cluster is coincident with both the mainshock nodal plane and the projection to depth of the fault plane imaged in the seismic reflection profiles.
The clear linkage between the earthquake and the imaged fault segment indicates that the Puente Hills blind-thrust system, which is not considered in current hazard models, is active and capable of damaging earthquakes.
structure.harvard.edu /sgat/SGATfault.html   (495 words)

 USGS Release: Major Losses of Up to $250 Billion Projected for Earthquakes on Puente Hills Fault Under Los Angeles ...
The Southern California Earthquake Center (SCEC) is a consortium funded by the National Science Foundation (NSF) and the USGS.
The new research results, published in the May 2005 issue of the Earthquake Engineering Research Institute´s Earthquake Spectra, were based on shaking scenarios created using newly available software for seismic hazard analysis developed by SCEC and the USGS, coupled with HAZUS loss-estimation software developed by the Federal Emergency Management Agency (FEMA).
The losses predicted for this event are greater than those experienced during the 1994 Mw 6.7 Northridge earthquake, both because of the higher potential magnitudes and because the heavily shaken area during Northridge was mostly wood-frame residential structures, whereas Puente Hills sits under older and more vulnerable commercial and industrial structures.
www.usgs.gov /newsroom/article.asp?ID=709   (955 words)

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