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Topic: Deep focus earthquake

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	Earthquake - Printer-friendly - MSN Encarta
		Seismologists examine the parts of an earthquake, such as what happens to the Earth’s surface during an earthquake, how the energy of an earthquake moves from inside the Earth to the surface, how this energy causes damage, and the slip of the fault that causes the earthquake.
		Earthquake waves begin to radiate out from the focus and subsequently form along the fault rupture.
		The properties of an earthquake depend strongly on the type of fault slip, or movement along the fault, that causes the earthquake.
	encarta.msn.com /text_761571674___18/Earthquake.html (883 words)

	World-Wide Tsunamis Introduction (Site not responding. Last check: 2007-10-23)
		Radiation of a remote-source tsunami from the focus of an earthquake is directional, depending on the geometry of the seafloor in the source region.
		Because this publication mainly lists those earthquakes that have caused death or damage, the number of earthquake reports is dependent on the written history available for a particular region, as well as on the rate of development of population centers and related structures.
		Earthquake epicenters and tsunami source locations may have been assigned to the wrong places when the names of localitieis were incorrectly transcribed or when some localities had identical or very similar names.
	www.ngdc.noaa.gov /seg/hazard/tsuintro.shtml (2364 words)

	Physics Today June 2001
		A large earthquake on a segment of a fault changes the stress on the adjacent segments, either statically or dynamically, and accelerates or decelerates seismic activity, depending on the fault geometry.
		During an earthquake, some energy is used to fracture rocks; this may be modeled in the spring system by attaching an arm to the spring that scratches the wall.
		Figure 5b suggests that the degree of criticality, analogous to the expectancy in the branching-model simulation, could, in principle, be diagnosed by measuring the slope of the magnitude-frequency relationship for the area.
	www.aip.org /pt/vol-54/iss-6/p34.html (3433 words)

	Measuring the Size of an Earthquake
		Shallow earthquakes are between 0 and 70 km deep; intermediate earthquakes, 70 - 300 km deep; and deep earthquakes, 300 - 700 km deep.
		The existence of deep-focus earthquakes was confirmed in 1931 from studies of the seismograms of several earthquakes, which in turn led to the construction of travel-time curves for intermediate and deep earthquakes.
		The most obvious indication on a seismogram that a large earthquake has a deep focus is the small amplitude, or height, of the recorded surface waves and the uncomplicated character of the P and S waves.
	earthquake.usgs.gov /learning/topics/measure.php (1811 words)

	Earthquakes
		An earthquake is when the surface of the earth is shaking because of rapid movement of the rocky outer layer of the earth.
		Shallow-focus earthquakes are created if the focus is near the surface of the earth (between zero and forty miles deep) while deep-focus earthquakes are created if the focus is deep within the earth (between forty and four hundred miles deep).
		Luckily, earthquakes that are extremely large only occur once every few years anywhere in the world, but moderate earthquakes (earthquakes with a magnitude of around 7.0 on the Ritcher scale) usually occur around twenty times a year.
	library.thinkquest.org /03oct/01027/earthquakes.html (1495 words)

	Savage Earth: Restless Planet
		Most earthquakes happen near the boundaries of tectonic plates, both where the plates spread apart and where they crunch or grind together (although large temblors also strike from time to time in the normally stable interior of continents).
		The calculation of Richter magnitude is based on the maximum strength of the vibrations (measured by a seismograph) and the distance of the instrument from the epicenter of the earthquake.
		Though some scientists dream of discovering warning signals that would allow the evacuation of a city just before a large earthquake, the focus of earthquake preparation today is on making sure that buildings and other structures are engineered to withstand the maximum likely shaking without collapsing completely.
	www.pbs.org /wnet/savageearth/earthquakes (1193 words)

	TONGA - THE EARTHQUAKE AND TSUNAMI OF MAY 3, 2006 IN TONGA - by Dr. George Pararas-Carayannis
		What was remarkable about this earthquake was a series of at least 50 strong but very deep aftershocks (Wiens and McGuire, 2000), The distribution of these aftershocks were to the NNE of the main event which indicated that this must have been the orientation of the rupture's propagation.
		Tsunamis along subduction zones are primarily generated by shallow earthquakes in the outer rise, where the crustal failure results fom tension caused by the downward bending of the oceanic plate into the trench.
		Most of the earthquakes occur at greater focal depths and - as already stated - none of the historical earthquakes are known to have generated a significant tsunami.
	www.drgeorgepc.com /Tsunami2006Tonga.html (1868 words)

	FOCUS Humanitarian Assistance
		Focus Humanitarian Assistance is an international group of agencies established in Europe, North America and South Asia to complement the provision of emergency relief, principally in the developing world.
		Focus Humanitarian Assistance is affiliated with the Aga Khan Development Network, a group of institutions working to improve opportunities and living conditions, for people of all faiths and origins, in specific regions of the developing world.
		Focus Humanitarian Assistance has been playing a critical role in coordinating and assisting emergency relief operations in the aftermath of the earthquake which struck several parts of Pakistan on 8th October 2005.
	www.akdn.org /focus (495 words)

	[No title]
		An earthquake is a sudden shaking or rupture in the earth caused by the release of accumulated stresses in the crust.
		The focal depth of an intermediate focus earthquake ranges from 70 to 300 km., and that of a deep focus earthquake from 300 to 800 km.
		Intensities are quantified using a scale(here in Philippines, we used PHIVOLCS Earthquake Intensity Scale), which has numerical values ranging from I to X. After the numbers are assessed at various localities, a contour map, known as the isoseismal map, is prepared depicting regions of equal seismic intensity.
	www.phivolcs.dost.gov.ph /soepd2/earthquakes/geninfo.html (839 words)

	Problems with plate tectonics
		Deep earthquakes are disconnected from shallow ones and there are very few intermediate earthquakes (Figure 6).
		For instance, four strong deep-focus earthquakes have occurred 75 to 200 km west of the Kurile-Kamchatka subduction zone, and were attributed to a detached piece of subducted lithosphere that is still deforming.
		Another disconcerting development for PT is that the slip motion of earthquakes rarely occurs in the direction of the dip of the Wadati-Benioff zone; it is commonly oblique to the "subduction" plane (Oard, 2000b; Suzuki, 2001b).
	ourworld.compuserve.com /homepages/dp5/lowman.htm (6123 words)

	Earth Quake
		Earthquakes were rare in the area prior to construction of the dam, but seismographs registered at least 600 shallow-focus earthquakes between 1936 and 1946.
		Volcanic earthquakes are caused by the upward movement of magma under the volcano, which strains the rock locally, and leads to an earthquake.
		Earthquakes that occur in the area surrounding the Pacific Ocean, at the edges of the Pacific plate, are responsible for an average of 80 percent of the energy released in earthquakes worldwide.
	members.fortunecity.com /phylcage/past/events/earthquake.htm (4152 words)

	Free-ResearchPapers.com - Earth Quake Reference Files
		Volcanic earthquakes are caused by the upward movement of magma under the volcano, which strains the rock locally, and leads to an earthquake.
		After studying the worldwide distribution of earthquakes, the pattern of earthquake types, and the movement of the earth’s rocky crust, scientists proposed that plate tectonics, or the shifting of the plates as they move over another weaker rocky layer, was the main underlying cause of earthquakes.
		Earthquakes within plates, or intraplate tremors, are rare compared with the thousands of earthquakes that occur at plate boundaries each year, but they can be very large and damaging.
	www.free-researchpapers.com /dbs/b8/sff323.shtml (5512 words)

	[No title]
		Most earthquakes are powered by the release of the elastic strain that accumulate over time, typically, at the boundaries of the plates that make up the Earth's lithosphere via a process called Elastic-rebound theory.
		Deep focus earthquakes, at depths of 100's km, are possibly generated as subducted lithospheric material catastrophically undergoes a phase transition since at the pressures and temperatures present at such depth elastic strain cannot be supported.
		The largest earthquake in any series of earthquakes; to be definitively called a "mainshock", it should generally be at least half a magnitude unit larger than the next largest quake in the series.
	www.lycos.com /info/earthquakes--quakes.html (556 words)

	Deadly Earthquakes (Site not responding. Last check: 2007-10-23)
		Math: Earthquakes are often remembered in the public consciousness not for the actual magnitude of the quake, but for the resulting death toll and the amount of destruction caused.
		Have students work the Tangible Math activity, Earthquakes, to learn if there is a direct correlation between the magnitude of an earthquake and the death toll.
		When a quake occurs deep in the Earth, the planet itself acts as a buffer, absorbing energy; but when the quake occurs closer to the surface, the planet surface and human-made structures absorb the energy.
	www.riverdeep.net /current/2002/04/040102t_earthquakes.jhtml (1299 words)

	CBC News Indepth: Forces of Nature - Earthquakes
		An earthquake survivor is tended to inside a tent set on the grounds of Bordj Menaiel hospital east of Algiers, on Saturday, May 24, 2003, three days after the quake that killed almost 1,800 and wounded thousands more.
		An earthquake is one of the most destructive events in the natural world.
		The first practical scale for measuring earthquakes was developed by geologist Charles Richter at the California Institute of Technology in the 1930s, and the scale that most scientists use today still bears his name.
	www.cbc.ca /news/background/forcesofnature/earthquakes.html (1234 words)

	Straight Up \| Jan Herman:
		In the Russian silent movies, and in the American cinema of the thirties, depth of field -- the amount of the frame that was in sharp focus -- was generally shallow, and filmmakers used lighting and editing to direct our attention to the most significant part of the action; the rest was blurry, mere background.
		Deep focus, Bazin said, liberated the spectator from the coercion of montage.
		From what rudimentary optics I know, increasing the depth of focus of a lens depends on increasing the "f" stop (i.e., closing down the iris), which requires boosting the lighting of the scene to compensate for darkening the exposure.
	www.artsjournal.com /herman/archives/2006/02/deep_focus_es_c_1.html (1951 words)

	AGU Web Site: Deep Bolivian Earthquake
		While big earthquakes typically wreack havoc for humankind, the biggest deep earthquake ever recorded - the magnitude 8.3 event that occurred 637 km beneath the surface of Bolivia on June 9, 1994 - has brought enlightenment - of sorts.
		By analyzing the frequency oscillations from deep events, scientists have been able determine the density and related properties of rock in various parts of the mantle.
		Determining the geometry of the fault plane is another way that scientists attempt to decipher the puzzle of deep quakes, in particular of the physical mechanism.
	www.agu.org /sci_soc/bolivian.html (1205 words)

	Past Exams Page
		Earthquake control is an attempt to modify the nature of occurrence of earthquakes on known active faults.
		Most of the earthquakes that have occurred in the world are (a) shallow earthquakes, (b) intermediate earthquakes, and (c) deep earthquakes.
		Earthquake control means (a) elimination of all earthquake occurrences, (b) to trade off large earthquakes for a great number of small and undamaging ones, (c) shifting the possible epicenters of large earthquakes away from the populatoin, (d) to cement up the faults.
	www.usc.edu /dept/LAS/factech/teng/practice_exams.html (6910 words)

	[No title]
		Earthquakes are divided into two types based on the depth of their focus (Zobach, 1996).
		Earthquakes occurring at 70 to 700 kilometers are deep focus events; they are not as common.
		Earthquakes are known to produce fissures, cracks in the land that can range from centimeters to meters in width (Milne, 1939).
	keller.clarke.edu /~english/honors/jen (2479 words)

	Parkfield Borehole Network
		Detection, monitoring, and high-resolution recording of earthquakes down to the smallest possible magnitudes with the highest possible signal-to-noise (especially in the region of the proposed SAFOD drilling) is a major objective of the HRSN data collection.
		However, during earthquakes, data compression is lower due to the higher amplitude signals of the quakes.
		Information on the details of the local deep fault zone structure are also contained in the wave fields of energy generated by distant teleseismic events.
	seismo.berkeley.edu /annual_report/ar01_02/node9.html (4218 words)

	Hiroo Kanamori (Site not responding. Last check: 2007-10-23)
		While accurate earthquake predictions are difficult, these systems aid in the post-earthquake response and recovery phases, and thus are socially beneficial in modern industrialized urban and suburban regions.
		Eissler, H., and Kanamori, H., 1982, A large normal-fault earthquake at the junction of the Tonga trench and the Louisville ridge: Phys.
		Kanamori, H., 1983c, Mechanism of the Coalinga earthquake determined from long-period surface waves in the 1983 Coalinga, California earthquakes, in Bennett, J.H., and Sherburne, R.W., eds., California Department of Conservation, Division of Mines and Geology: Sacramento, p.
	www.gps.caltech.edu /faculty/kanamori/kanamori.html (7573 words)

	EARTH QUACKE
		The destruction an earthquake causes depends on its magnitude and duration, or the amount of shaking that occurs.
		Earthquakes, or seismic tremors, occur at a rate of several hundred per day around the world.
		Fault rupture is not the only cause of earthquakes; human activities can also be the direct or indirect cause of significant earthquakes.
	www.angelfire.com /ky3/abeer/earth_quacke.htm (1665 words)

	EvC Forum: Geology Glossary
		A zone of deep-focus earthquakes that dips away from a deep-sea trench and slopes beneath the adjacent continent or island arc.
		An earthquake with a focus located at a depth between 70 and 300 km.
		A soil that is rich in oxides of iron and aluminum formed by deep weathering in tropical and subtropical areas.
	www.evcforum.net /WebPages/Glossary_Geology.html (7529 words)

	Rupture Characteristics of the Deep Bolivian Earthquake of 9 June 1994 and the Mechanism of Deep-Focus Earthquakes -- ... (Site not responding. Last check: 2007-10-23)
		Rupture Characteristics of the Deep Bolivian Earthquake of 9 June 1994 and the Mechanism of Deep-Focus Earthquakes -- Silver et al.
		Rupture Characteristics of the Deep Bolivian Earthquake of 9 June 1994 and the Mechanism of Deep-Focus Earthquakes
		Rupture of the Large (Mw 7.8), Deep Earthquake of 1973 Beneath the Japan Sea with Implications for Seismogenesis.
	www.sciencemag.org /cgi/content/abstract/268/5207/69 (384 words)

	[No title]
		Earthquake, shaking of the earth’s surface caused by rapid movement of the
		earthquakes are caused by the upward movement of magma under the volcano, which
		earthquake is by measuring the earthquake’s seismic magnitude, or the
	www.yourlearningzone.com /Geography/Earthquakes.html (4297 words)

	The AS-1 Seismograph – Magnitude Determination and Calibration
		Estimating Earthquake Magnitude from AS-1 Seismograms: Magnitude is an estimate of the energy release or size of an earthquake.
		Magnitude estimates are calculated from the amplitude of wave energy on a seismograph adjusting for the distance of the seismograph station from the earthquake (seismic waves spread out and are absorbed during propagation and thus generally become smaller at greater distances from the earthquake epicenter) and the amplification of the signal by the seismograph.
		) and for earthquakes of particular depths (for example, surface wave magnitudes are only valid for shallow focus earthquakes) or magnitude (body wave formulas are inaccurate for very large earthquakes).
	web.ics.purdue.edu /~braile/edumod/as1mag/as1mag3.htm (951 words)

	Geology 150 - Earthquake Questions
		48: Most earthquakes are generated in the upper ________km of the earth.
		49: Shallow focus earthquakes occur from _______ to _______km.
		53: The "magnitude" of an earthquake is a measure of __________________________
	www.calstatela.edu /faculty/acolvil/quest1.html (638 words)

	Plot That Quake! Earthquake Maps & Lists
		Note: In these figures, the earthquakes are not plotted in time order.
		Because the number of shallow earthquakes exceeds the number of deep events, we have plotted the intermediate and deep focus events last.
		Other examples of template maps and earthquake lists may be found in the earthquake plots created from the CNSS catalog.
	www.seismo.berkeley.edu /seismo/istat/digiguide/EQmaps.html (174 words)

	What is exploding 400 miles beneath our feet?
		Most deep-focus earthquakes occur near subduction zones, where the science of plate tectonics says that the earth's crust is diving below another crustal plate.
		If the rocks that far down cannot break to created earthquake shocks, perhaps there are explosions of some sort.
		Complicating the problem are those few deep-focus earthquakes that shake the planet's innards in locations where there are no plates being thrust down into the earth's interior.
	www.science-frontiers.com /sf062/sf062g11.htm (435 words)

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