what is the minimum number of siesmic stations needed to determine the location of the epicenter of earthquake
346643
Triangulation of a seismic epicenter requires three different measurement stations.\n\nWith two measurements, you come down to two possible locations.  The third measurement is required to select one of the two and reject the other.\n\nhttp://search.yahoo.com/search?p=triangulation+seismic+epicenter&ei=UTF-8&fr=slv1-wdgt&x=wrt\n\n(Note that the original "triangulation" did not require three points.  If you want to measure something off in the distance, you only needed two reference points and the distance between them to measure the third.  Say if you had two towers and wanted to measure the distance to a hill, you could do it with two reference points drawing out a triangle.  In this case "triangulation" requires three points ot measure a fourth point.  In reality, I think it should be called trilateration or multilateration but I think the term "triangulation" has stuck to mean any form of estimating an unknown using several reference points for guidance.)\nhttp://en.wikipedia.org/wiki/Triangulation\nhttp://en.wikipedia.org/wiki/Trilateration\nhttp://en.wikipedia.org/wiki/Multilateration
711008
I think it depends on what's near it to be destroyed, and whether it starts one or more tsunamis and how big they are & where they hit. A bigger quake certainly has greater potential for destruction.
234732
X times Y^Z\nexample\n1 x 10^8.3 = magnitude 8.3 quake
376357
there are many earthquake observatories in japan.\n we can get almost correct information within 10minutes\n but sometimes we cannot count on the machines.earthquakes\n occur everyday.
224482
The seismic shadow zone is a range of angular distance from a seismic event where the P- (primary, or compression) and S- (secondary, or shear) waves cannot be detected. The range is 104 to 140 degrees from the epicenter. The shadow is due to opacity of the earth's liquid core to shear waves and refraction by the outer core of compression waves. The ref. contains a good explanation and illustration.
685931
http://earthquake.usgs.gov/eqcenter/recenteqsww/
55918
An earthquake is the shaking of the ground caused by an abrupt shift of rock along a fracture in the Earth, called a fault. Within seconds, an earthquake releases stress that has slowly accumulated within the rock, sometimes over hundreds of years. ... \nThe size of an earthquake is indicated by a number called its magnitude. Magnitude is calculated from a measurement of either the amplitude or the duration of specific types of recorded seismic waves. Magnitude is determined from measurements made from seismograms and not on reports of shaking or interpretations of building damage. ... The intensity of and earthquake is a measure of the amount of ground shaking at a particular site, and it is determined from reports of human reaction to shaking, damage done to structures, and other effects. ... \n\nEarth scientists believe that most earthquakes are caused by slow movements inside the Earth that push against the Earth's brittle, relatively thin outer layer, causing the rocks to break suddenly. This outer layer is fragmented into a number of pieces, called plates. Most earthquakes occur at the boundaries of these plates. In Washington State, the small Juan de Fuca plate off the coast of Washington, Oregon, and northern California is slowly moving eastward beneath a much larger plate that includes both the North American continent the land beneath part of the Atlantic Ocean. Plate motions in the Pacific Northwest result in shallow earthquakes widely distributed over Washington and deep earthquakes in the western parts of Washington and Oregon. The movement of the Juan de Fuca plate beneath the North America plate is in many respects similar to the movements of plates in South America, Mexico, Japan, and Alaska, where the world's largest earthquakes occur. ...
422794
Whan an earthquake occurs, it sends shock waves through the earth. One travels through the earth's surface by compressing back and forth the rocks, the other by moving them up and down. These both travel at different but known speeds, so when an earthquake registers at a recording site it registers as two blips, a P wave blip first and an S wave blip later. The distance between these blips tells the seismologists how far away the earthquake was, the bigger the gap, the further the distance. To find the location of the earthquake you then need to use different recording sites data for how far away it was and triangulate the data to find an actual location of the epicentre. The waves also travel through the earth in different ways in addition to the p and the s waves, by going throught the surface or more directly through the earths core. Again the data for these echo times differences is known and allows a distance to the epicentre to be calculated.
362562
Well, to avoid tsunamis and typhoons/hurricanes you need to be in a landlocked country. To avoid tornadoes you need something fairly mountainous. As for earthquakes, you need to avoid fault lines. I would guess somewhere in Germany or thereabouts.
717054
Try: http://earthquake.usgs.gov/research/monitoring/anss/ for definitions.
870278
The first link provides current and historical information regarding the fault.  The second link is to the history channel's web site which contains a brief overview of the Mega Disaster's episode on a possible future fault movement.\n\nhttp://quake.ualr.edu/public/nmfz.htm\nhttp://www.history.com/minisite.do?content_type=Minisite_Episodes&content_type_id=1435&display_order=3&mini_id=1401
369527
The 1997 Uniform Building Code set the standard on seismic design for buildings.  You might try searching for that on Yahoo!
1041920
The scientists are saying that a "big one" is going to happen. It's not a question of "if", its "when." And they don't know when, it is still, unfortuneatley, impossible to predict earthquakes. They have specials on this topic on the Discovery Channel, so check out your local listings so you can see. I think there's even a movie. Anyways, there is also a huge fault by Washington.
280851
Since the Richter scale is logarithmic, a 6.0 earthquake would have a relative magnitude of 10^6 (1,000,000), while a 7.0 earthquake would be represented by 10^7 (10,000,000), or ten times stronger.
1104626
One cannot provide solution without the longitude of local station...\nIt shall be atleast 2500 miles away...
1097840
The possibility exists.. The probability is low. \n\nFor what it's worth, It doesn't require a fault to have an earthquake. Keep that in mind. Shifting plate can happen over areas where tectonic plates are non existent. \n\nThere has been measurable earthquakes in the northeast since recording began. \nEven up to a magnitude 7.. \nBelow is a map of recorded historical earthquakes. \nhttp://earthquake.usgs.gov/regional/states/us_damage_eq.php
85265
Actually about two earth tremors are felt every year in Hong Kong. They are small, and less frequent than in other areas, however Hong Kong is NOT necessarily safe from earthquakes. \n\nThe nearest known plate boundary (of the Eurasian and Pacific plates) is about 600 km away, but there are still occasional midplate earthquakes that occur (seismologists do not know the origin of these). However, this does not mean that there is not some other fault nearby that has not revealed itself. Microplates near plate boundaries do exist, and sometimes these are surrounded by "locked" faults (because sufficient stress has not accumulated to overcome the resistance presented by asperities).  This can either mean that the chance of earthquakes is reduced, but it can also mean that if these asperities are overcome, the energy release can be substantial. \n\nThe Hong Kong government seismic observatory states that:\n\n"Several scientific studies carried out recently showed that in Hong Kong, the return period for an Intensity V (5) tremor would be 15 to 20 years and that for an Intensity VII (7) tremor would be 350 to 400 years." \n\nThe intensity scale is known as the Modified Mercalli Intensity Scale. An intensity of V corresponds to a magnitude of 4.3 to 4.8 on the Richter scale. An intensity of VII corresponds to a magnitude of 4.8 to 6.2 on the Richter scale.\n\nAccording to the official government of Hong Kong publication on earthquake hazards in Hong Kong:\n\n"Every year, about two earth tremors are felt in Hong Kong. To put this in context, studies into earthquake risk in Hong Kong carried out by the Geotechnical Engineering Office (GEO) classified the seismicity of Hong Kong and the adjoining Guangdong Province as "low to moderate". The earthquake hazard in Hong Kong is therefore considered to be very much lower than in areas such as Japan, Taiwan and the western USA which lie close to the earth's more seismically active zones along crustal plate boundaries. However, earthquake risk in Hong Kong cannot be regarded as negligible."