On Tuesday, January 17, at 5:46 a.m. local time, an earthquake of magnitude 7.2 (Richter scale) struck the region of Kobe and Osaka in south-central Japan.
On Tuesday, January 17, at 5:46 a.m. local time, an earthquake of magnitude 7.2 (Richter scale) struck the region of Kobe and Osaka in south-central Japan. This region is Japan's second-most populated and industrialized area, after Tokyo, with a total population of about 10 million. The shock occurred at a shallow depth on a fault running from Awaji Island through the city of Kobe, which in itself has a population of about 1.5 million. This was an unsuspecting city, scientist had doubted a big earthquake there since it was quite a distance from the point were the three-plate boundaries meet. Strong ground shaking lasted for about 20 seconds and caused severe damage over a large very area. Nearly 5,500 deaths were confirmed, with the number of injured people reaching about 35,000. Nearly 180,000 buildings were badly damaged or destroyed, and officials estimate that more than 300,000 people were homeless on the night of the earthquake. The life loss caused by the earthquake was the worst in Japan since the 1923 Great Kanto Earthquake, when about 140,000 people were killed, mostly by the post-earthquake conflagration. The economic loss from the 1995 earthquake may be the largest ever caused by a natural disaster in modern times. The direct damage caused by the shaking is estimated at over ¥13 trillion (about U.S.$147 billion). This does not include indirect economic effects from loss of life, business interruption, and loss of production. Damage was recorded over a 100-kilometer radius from the epicentre, including the cities of Kobe, Osaka, and Kyoto, but Kobe and its immediate region were the areas most severely affected since they were closest to the epicentre. Damage was particularly severe in central Kobe, in an area roughly 5 kilometres by 20 kilometres parallel to the Port of Kobe. This coastal area is composed primarily of soft alluvial soils and artificial fills. Severe damage extended well northeast and east of Kobe into the outskirts of Osaka and its port.
Liquefaction and Other Ground Failures
The earthquake caused extensive ground failures, which affected buildings, underground infrastructure, the port, highways, all types of other facilities on soft or filled ground, and hindered recovery efforts. Ground failures occurred primarily because of liquefaction, the result of loose, water-saturated sand being shaken during an earthquake and assuming a semi liquid/ liquid state. The areas affected by liquefaction were more heavily developed than any other earthquake-stricken region to date therefore the damage due to liquefaction was great. The affected areas were located primarily along the coastline and the numerous watercourses in ...
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Liquefaction and Other Ground Failures
The earthquake caused extensive ground failures, which affected buildings, underground infrastructure, the port, highways, all types of other facilities on soft or filled ground, and hindered recovery efforts. Ground failures occurred primarily because of liquefaction, the result of loose, water-saturated sand being shaken during an earthquake and assuming a semi liquid/ liquid state. The areas affected by liquefaction were more heavily developed than any other earthquake-stricken region to date therefore the damage due to liquefaction was great. The affected areas were located primarily along the coastline and the numerous watercourses in the general area of Kobe. Massive liquefaction and lateral spreading took place in areas of reclaimed land and on the many artificial islands in the city of Kobe and Nishinomiya. Ejected sand from liquefaction covered much of the islands and interfered with rescue and recovery operations.
The most obvious and destructive liquefaction and related lateral spreading of soils and settlement occurred along the dozens of kilometres of seawalls along the port because of the water soaked soils. Spreading of the liquefaction of 3 (or more in some places) meters and vertical settlement of 2 to 3 meters were observed along the seawalls throughout the Port of Kobe. The largest settlements, and worst damage, seemed to be associated with the older reclaimed lands, such as the older parts of the port. The newer, engineered fills performed somewhat better than did the old fills, but with less than adequate results. Numerous buildings on reclaimed land tilted because of ground settlement. These were primarily older, heavy concrete, industrial buildings. Most pile-supported buildings appeared to perform well, or large pile-supported buildings in areas where extensive occurred had little or no damage. Typically, the sidewalks of such buildings would settle 50 centimetres or more, but there would be no apparent damage to the buildings themselves. The same was generally true for newer highway structures supported on piles. However, the strong shaking may have exceeded the capacity of many pile foundations supporting elevated expressway and bridge piers, causing tilting which was observed to be as much as 2 meters. This often contributed to damage or collapse of the structures.
This is an example of one building falling where a newer building says upright with little damage.
Transportation
One of the most disturbing aspects of the earthquake was the severe, extensive damage to the transportation system. Kobe wasn't have the facility to let the much need help enter Kobe because of the earthquake's damage to highways, bridges, and rail systems resulting in major congestion and greatly impeded relief efforts. Many of these surface streets were also unusable, blocked by debris from collapsed structures and damaged by ground settlement. Forced use of alternative road or rail lines added hours to normally short trips. Damage to the transportation system had the potential to contribute greatly to the number of fatalities. Had the earthquake occurred during rush hour, there would have been many hundreds of fatalities on collapsed freeways, and numerous crowded trains would have derailed, in some cases plunging onto city streets. For example, built in the mid- to late 1960s, the Hanshin Expressway is the main through road and is almost entirely elevated for more than 40 kilometres. Much of the roadway is supported by single, large reinforced concrete piers spaced every 32 meters, many of which failed in shear or bending over a 20-kilometer length. Similar failures of the roadway occurred at many locations, including complete toppling of large reinforced concrete pillars supporting a 500-meter section. Elevated highways in Japan typically consist of single spans that have roller bearings at one end and are fixed at the other. To conserve valuable space, single-column, cantilever structures are common. Bearing widths on Kobe area expressways appeared to be inadequate in most instances.
Telecommunications
Telecommunications systems did very well in the earthquake, with very few service interruptions. Telephone service was available on a limited basis in the most heavily damaged areas on January 18, although a week after the earthquake, more than 25,000 telephone lines were still disconnected in the 18 municipalities hardest hit. More than 2,000 telephones were installed for public use at shelters and public offices.
Water
The Kobe area had a water system designed to be operable after earthquakes. There are approximately 30 reservoirs supplying water to the Kobe area through a gravity-fed system. Of these, 22 reservoirs had automatic emergency shutdown valves and multiple storage tanks. In the event of an earthquake, these valves are designed to automatically shut off water flow out of half of the reservoir tanks. All 22 valves tripped and worked correctly. This enabled 30,000 cubic meters of water (8 million gallons) to be stored in reserve in the reservoirs equipped with automatic shutdown valves. But, As a result of extensive ground settlement and other failures, underground water pipelines were severely damaged in the earthquake, with approximately 2,000 breaks resulting in general lack of service in Kobe. The massive damage to the water transmission lines caused the tanks without automatic shutoff valves to drain in the first 1 to 8 hours after the earthquake. By the time the fires had started, much of the unreserved water had already drained from the system. With the transmission lines destroyed, the reserve water was also unavailable for fire fighting.
Gas
The gas system had at least 1,400 breaks in its underground distribution system, primarily at service lines, with general curtailment of service by Osaka Gas Company to 834,000 households. Japanese buildings and homes have automatic gas shutoff systems, but many failed to work because of building collapses, other building damage, and broken pipes. The population in the heavily impacted areas was also notified to expect no gas service for about two months. Also, with the broken gas pipes spewing out gas, all it needed was a spark to set the either city alight, which is what happened, the fire spread quickly causing lots more damage after the earthquake had finished, this was made worse with the rubble impeding the fire-fighters from putting out the fire.
Tectonic Activity
Kobe is located farther than many other cities in Japan from the dangerous three tectonic plates (the Pacific, Eurasian, and Philippine). This triple junction is a junction of three compressive subduction zones. Causing many earthquakes in Japan. This was also the cause of the Kobe earthquake.
Time of day
The time of day would have an effect on the impact as well, it shook the ground at 5:40 in the morning, that means people would just be getting up so everyone would be indoors. If everyone was indoors the collapsing buildings would be full of people, adding to the death toll. People cooking breakfast would set alight the gas that was leaking out about the city after the earthquake. This is probably what caused the fire in many places
