anyone know any facts about the japanese kobe earthquake ?
how it was caused, reponses to it, lessons that can be learnt, and the effects of it
coz im interested … ummm ? 🙂
Yes and i am a boring clown….
Kirsten this may help you forgive my spelling and lying about being a boring clown too;
concerning Kobe earthquake may i first say: The effects of any earthquake depend on a number of different/ varying factors. These factors are all of:
Intrinsic to the earthquake – its magnitude, type, location, or depth;
Geologic conditions where effects are felt – distance from the event, path of the seismic waves, types of soil, water saturation of soil; and
Societal conditions reacting to the earthquake – quality of construction, preparedness of populace, or time of day (e.g.: rush hour).
One can count the number of deaths caused by large earthquakes to compare the results of all these disparate factors in combination. The Oct. 17, 1989 Loma Prieta earthquake occurred in the least-populated area of the generally urban San Francisco peninsula. Construction standards in the area are relatively high, and the populace relatively prepared. However, soft, highly-saturated soils near San Francisco Bay caused some spectacular failures of large highway structures unusually far away from the event. Even though it was rush hour, many fewer cars were on the roads due to the start of the opening game of the World Series, being played locally. Thus deaths were limited to about 75.
On the other hand, the same year an earthquake of nearly identical energy struck the war-torn country of Armenia, between Russia and Turkey. It was located much closer to the major cities of the region, where poorly-engineered houses of unreinforced concrete collapsed on their occupants during the night. The number of fatalities passed 25,000.
*******Jan. 17, 1995 Hyogo-Ken Nanbu Earthquake
The worst earthquake catastrophe in years occurred on western Honshu Island early this year. More than 5000 people perished in southern Hyogo prefecture, most in the city of Kobe,
KOBE Japan’s most important port. The loss of so many lives, in a country where so much effort had been made to prepare for earthquakes, shocked observers worldwide. However, the magnitude of this catastrophe is probably due to a terrible coincidence of a few simple seismological and societal factors, which may become clear in the photos below.
(from the USGS) Kobe is located farther than many other cities in Japan from the dangerous intersection of three tectonic plates: the Pacific, Eurasian, and Philippine. This triple junction is a junction of three compressive subduction zones. The red-hatched areas above are the parts of the subduction fault that had aleady broken in great earthquakes in 1944 and 1946. Kobe is also somewhat off the Median Tectonic Line, a zone of strike-slip faults.
(from the Earthquake Research Institute, Tokyo) This map shows the epicenters of the earthquake’s aftershocks within the first two days afterward. Decades of observation show that the most reliable way to locate the fault that broke in any earthquake is to observe where aftershocks are concentrated. This map shows that the earthquake fault obliquely cut the north side of Awaji Island, and cossed the bay to run along the Honshu coast directly below the city of Kobe. Probably the most important coincidence leading to the mass casualties was this “direct hit” of the city by such a large faulting event. There was no intervening distance to mitigate the effects. The Northridge area of Los Angeles suffered a similar coincidence in January 17, 1994.
There are two classes of earthquake effects: direct, and secondary. Direct effects are solely those related to the deformation of the ground near the earthquake fault itself. Thus direct effects are limited to the area of the exposed fault rupture. Many earthquake faults (such as at Northridge) never break the surface, ruling out direct effects. In the Hyogo-Ken Nanbu event, surface rupture of the fault was observed only in a rural area of Awaji Island, with displacements of up to 3 meters. Few structures were near enough the fault to be damaged by the displacement, although underground utilities, fences, and irrigation ditches were cut. Rice paddies were thrown far out of level.
(taken by the Geographical Survey Institute of Japan; used by permission.)
Aerial view of the fault rupture on northern Awaji Island, taken on January 18th, the day after the event. From left to right along the rupture, a landslide from the rupture covers a road; a fault scarp across a rice paddy; a right-lateral offset in a dirt road (inset); and three more pointers to the scarp. Note how little damage there apparently is to homes even very close to the fault.
(from a report by J.-P. Bardet at USC and others at Gifu Univ.; used by permission)
View along the fault scarp on Awaji Island. The section of rice paddy to the right has been uplifted by more than one meter. Note the cut road in the foreground. It is often possible to measure the displacement and length of the exposed fault rupture to estimate the slip and area of the subsurface fault, providing an independent estimate of the earthquake’s magnitude.
Photo from the Japanese edition of Newsweek showing the fault scarp. Note the horizontal as well as vertical offset shown by the dike in the rice field. Well-built structures often escape major damage even so close to a seismogenic fault.
Elastic rebound, the permanent deformation of the ground due to the fault rupture, will extend many kilometers from the fault itself, and is often measurable even where the rupture itself remains buried. In the past geodesists have had to make painstaking and expensive surveys, visiting hundreds of field sites, to measure deformation of an area struck by an earthquake.
(analyzed by the Geographical Survey Institute of Japan and the National Space Development Agency of Japan; used by permission.)
Lately planetary geophysicists have developed a quick way to make a map image of deformation using satellite radar interferometry. They compare satellite microwave-radar images of a region taken before and after the event. Any area displaced toward or away from the spacecraft’s positions will form an interference pattern, tracing out contours of equal displacement. The map image above of Awaji Island shows eight or more colored interference fringe lines approaching the fault, at 11 cm of vertical displacement per fringe contour, demonstrating almost 1 meter of uplift by the earthquake. At left, two fringes parallel the coast through the city of Kobe, showing about 20 cm of displacement across the city from the buried fault.
Most of the damage done by earthquakes is due to their secondary effects, those not directly caused by fault movement, but resulting instead from the propagation of seismic waves away from the fault rupture. Secondary effects result from the very temporary passage of seismic waves, but can occur over very large regions, causing wide-spread damage. Such effects include: seismic shaking; landslides; liquefaction; fissuring; settlement; and the triggering of aftershocks and additional earthquakes.
(from the Architecture Dept. Of Tokyo Metro. Univ.) Since seismic waves spread out from their source just like ripples on a pond, they get weaker the farther you get from the earthquake. The ground acceleration versus distance plot at left shows this effect near Kobe. An acceleration of 1000 gal for seismic waves in the ground would be equal to the acceleration of gravity; so if it acted straight up it would be able to throw any object into the air. These accelerations are mostly from side-to-side, so even at only 50% of the acceleration of gravity are capable of toppling anything standing. Note that the recorded acceleraction can vary by a factor of two or three, especially near the fault.
(compiled by the Earthquake Research Institute, Tokyo) The great differences in secondary effects even between adjacent localities is shown by this map of instrumentally-recorded ground accelerations and velocities. Although the measurements do fall with distance from the epicenter, adjacent sites can vary by more than 50%. Such variation is usually caused by variation in the soil conditions.
(from the Architecture Dept. Of Tokyo Metro. Univ.) The seismograms above were recoded at two different sites near Kobe. On the left are three records of the sharp pulse, lasting less than 15 s, recorded at a station founded in relatively solid rock. On the right are three records of the strong and extended shaking, lasting two or even three minutes, at sites near the coast having soft, thick, water-saturated soils. The geological conditions right at a particular site play a crucial role in the strength, and length, of seismic shaking that can be experienced there. In all earthquakes, low-lying areas having soft, water-saturated soils experience by far the most damage.
Since most seismic shaking is side-to-side, a shaken structure will undergo shear as this house front in Kobe did. Shear is the bending of right angles to other angles. As it is much more difficult to shear a triangle than a rectangle, effective seismic design requires triangular bracing for shear strength.
(from Kobe University) This wooden house collapsed during the seismic shaking. It is likely that its heavy roof of ceramic tile created more shear force than its wood frame was built to resist. Tile roofs are popular in Japan.
Photo = 🙁 and with new hope 🙂
I am born Jewish and prayed to let Jesus into my heart, John chapters 3 & 10 favorite colors light green purple, and black white and pink all together with popcorn and Jelly beanies hehe, but i love Jesus the bestest
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