Kobe Earthquake
By Marc Frost
Why was the Kobe earthquake so devastating and how can the situation be improved for future earthquakes?

Introduction
Japan suffered one of its most devastating earthquakes in 1995. It was the Kobe Earthquake, also known as The Great Hanshin Earthquake because of the amazing damage done to the Hanshin Highway. This was the worst earthquake to hit Japan since The Great Kanto Earthquake in 1923.

What caused this earthquake to be so devastating? The combination of three subduction zones, old buildings, condensed population, fires, and liquifaction made it a sad day in Japan.

Tectonic Plates and the Nojima Fault.
Japan is right on three tectonic plates: the Eurasian Plate, the Philippine Plate, and the Pacific Plate (Figure A). The Nojima fault is a strike-slip fault which moved approximately 1.5 meters horizontally. The Kobe earthquake measured 7.2 on the Richter Scale and lasted for twenty seconds. The epicenter was 20 kilometers beneath Awaji island. Kobe is the closest major city, so that is where most of the damage occurred.

kobeplates.jpg
Figure A. Kobe lies close to three tectonic plates. (www.georesources.co.uk)

Structures
300,000 people became homeless, 26,000 were injured and over 5,000 people died. Most of these were the result of heavy 2 ton roofs collapsing. Many buildings were made out of light wood frames and could not support the heavy roofs during the earthquake. Some high rise building collapsed at the fifth floor because old building codes allowed for weaker superstructures starting at the fifth floor. Parts of the Hanshin Expressway were twisted nearly 90 degrees (Figure B). Several of the buildings built in Kobe after 1980 (before the earthquake happened) were built with stricter design codes, and most of these structures were still standing after the earthquake.

hanshin_express.jpg
Figure B. Hanshin Expressway.(www.ce.washington.edu)

Fire
Ruptured gas lines caused more than 300 fires to erupt. The approximately 300 fires that broke out following the earthquake caused some of the greatest devastations including massive water shortages. This large number of fires exceeded the capacity of firefighting resources and caused a number of devastating chains of events. Many firefighters could not reach fire zones because the roads were out and other utilities were down. The fire spread quickly due to many of the buildings being made of wood (Figure C).

kobe-burn2.GIF
Figure C. Broken gas lines caused several fires. (www.seismo.unr.edu)

Liquefaction
The earthquake also caused liquefaction to occur because Kobe is one of the world's largest ports. Several areas of the city suffered severe damage due to weak soil. Weak soil is formed when there is strong seismic shaking. The shaking breaks up sand particles in saturated soil and it looses both contact and friction. The soil then has no strength to carry anything heavy. In this case, the port was an extremely heavy load, which was one of the reasons why there was so much damage. For example, bridges collapsed, streets crumbled (Figure D), and buildings were left leaning.

portgraben.jpg
Figure D. Result of Liquefaction. (www.ce.washington.edu)

Aid
Damaged roads and railways made it difficult for help to arrive. Telephones in the area were out of order which made it difficult to communicate. Many areas were also without electricity and water. Japan also refused outside aid for a long time. On the positive side, over one million people aided in the recovery.

Several local hospitals struggled to keep up with the demand for medical treatment because of the collapsed roads; these did not allow supplies and personnel from reaching the damaged/affected areas. It is not surprising to know that many had to wait in corridors due to overcrowding. Many, unfortunately, had to be operated in waiting rooms and in corridors. Yes, Japan had refused outside aid but there were numerous who were willing to volunteer and they had to give in. Volunteer efforts to help the earthquake victims were so widespread that 1995 has been called "Japan's Year of the Volunteer." Just to give you an idea of the great hearts that were willing to help those in need, there were about 1.2 million volunteers who were involved in relief efforts during the first three months after the earthquake. Companies such as NTT and Motorola were generous enough to provide free telephone service for the victims since telephones in the area were out of order at the time.

Future Solutions
Many things went wrong during the kobe earthquake, and while Japan can't do much about its dangerous location to three tectonic plates, there is lots of room for improvement in earthquake safety for the future. To avoid fires, current technology should be able to shut off gas from underground pipe lines. In order for help to arrive quickly, Japan should improve the quality of its roads to resist shaking. Water and food needs to be stored in cases of emergencies. Kobe's residents would have a hard time not building on soil that isn't susceptible to liquefaction because it's a port city. To combat liquefaction, buildings should be built on sturdy foundation mats which would allow them to stand straight should the soil underneath liquefy (Figure E).
Today Japanese authorizes, have established better structural codes and building techniques, they have also designed special disaster prevention routes and reinforce the roads and surrounding buildings to remain intact during future earthquakes. Emergency food and water supply networks have also been established.

strongmat.gif
Figure E. Strong foundation mat. (www.ce.washington.edu)

Prior to the event, Japan prided itself in being well prepared for earthquakes. However, that wasn't the case. Whether Japan's post-Kobe improvements in earthquake standards are up to the task or not will only be known when the next big one hits.

Sources:
http://www.seismo.unr.edu/ftp/pub/louie/class/100/effects-kobe.html
http://www.ce.washington.edu/~liquefaction/html/quakes/kobe/kobe.html
http://www.ce.washington.edu/~liquefaction/html/how/how1.html
http://www.vibrationdata.com/earthquakes/kobe.htm
http://www.georesources.co.uk/kobehigh.htm
http://www.niksula.hut.fi/~haa/kobe.html
http://www.dis-inc.com/kobe.htm
http://en.wikipedia.org/wiki/Great_Hanshin_earthquake


Written by Marc Frost




Writen By Jessica Franzone


Kobe is one of Japan's major ports and is the capital of Hyōgo Prefecture. This is located on the island of Honshū which is the considered the mainland of Japan. Although the 1995 Earthquake destroyed much of this important port city, it is still recognized as one of the top four busiest ports in Japan.
In memoriam of the devastating earthquake that destroyed the city of Kobe, there is an annual illumination festival. It is called the Luminarie and it was first held in December 2005. Because of the two and a half million visitors who came and viewed the wonderful display of lights it has continues every year after (Figure F).

2005-kobe-luminarie1.jpg
Figure F. The lights from the Luminarie

Seismograms were located in many different areas in Kobe and according to these records; you can see that the geological conditions of the site is important to the damage the area obtains. Many parts of the area were mostly solid rock which indicated sharp pulse motions lasting at least 15 seconds. In areas that were soft and water saturated, there was recorded strong and extending shaking for up to two or three minutes. So the areas that were mostly likely more along the coast (with water saturated soils) experience the most damage.

http://apike.ca/japan_kobe_luminarie.html
http://www.seismo.unr.edu/ftp/pub/louie/class/100/effects-kobe.html


Features of a Strike-Slip Fault (Written By Joe Oh)

A strike-slip fault produces a shear movement that occurs on a horizontal axis. Movement of a strike-slip fault causes either a right or left-lateral movement. Many strike-slip fault can be found on transform plate boundaries. Depending on the fault, strike-slip fault can also have steps in them. A left stepping right-lateral fault will produce hills whereas a right stepping, right-lateral fault will produce basins.faultbends.gif

Costs of the Kobe Earthquake (Written By Joe Oh)

The island nation of Japan has one of the most dense population rates in the world. Because of this, there are many building that are closely packed together and the nation itself is also built on an area that is highly prone to liquefaction. Upon the shockwake of the earthquake, buildings started to sway in resonance with the frequency of the shaking of the earth. This caused many building to collide with each other. The Kobe Earthquake caused approximately ten trillion yen or $200 billion USD in damage, 2.5% of Japan's GDP at the time. At the time of the incident, the Kobe Earthquake was listed in the Guinness Book of Records as the "costliest natural disaster to befall any one country."

Aerial View:
Aerial view of faulting
Aerial view of faulting

taken by the Geographical Survey Institute of Japan; used by permission

One of the important concept of the Kobe earthquake was the rupture that occured in the fault. This is a very unique effect that happened during this earthquake which produce other significant events after the earthquake. A day later as they took down of all the damege caused by earthquake Kobe the geologist notice a huge rupture around the fault as states in J.Louie article the The Earthquake Effects in Kobe which caused a major landslide close to were the fault rupture. In the Aerial view (above) you could see the rupture from left to right. As stated by J.Louie "Note how little damage there apperently is to homes even very close to the fault." This rupture was very significant to the earthquake in expressing how much release of energy was expelled from the fault to cause the fault to rupture.

Reference:
J. Louie
http://www.seismo.unr.edu/ftp/pub/louie/class/100/effects-kobe.html





http://en.wikipedia.org/wiki/Great_Hanshin_earthquake
http://www.tulane.edu/~sanelson/geol204/eqcasehist.htm

Since the Kobe earthquake Japan has become one of the leaders in the technology of earthquake prevention. Seismic sensors are all over Japan ready to detect the next big one before the major shaking begins. The BBC article states, “"If we can detect the seismic wave at a station very close to the epicenter, and then analyze and estimate the seismic intensity and the arrival time of the wave, and if we can disseminate that information to the public, then people can get ready for strong motion before it arrives (Hogg)." This technology senses the initial P wave which occurs before the surface waves which is when the massive shaking occurs. The sensor can immediately send the detection, but the big struggle is giving that crucial information to the people, and fast. Television stations will instantly relay the warning, and, “People can also buy alarm systems connected via the internet to the Meteorological Agency systems (Hogg).” The biggest obstacle is warning as many people as possible in seconds to prevent the death and destruction that we all saw after the Kobe Earthquake.
Reference

Hogg, Chris. "Japan's new quake detection system." BBC NEWS Online. 7 Dec. 2008. <http://news.bbc.co.uk/2/hi/asia-pacific/7062128.stm>.
Written by cdbac