Tohoku Japan Earthquake
3/11/2011 10:15:00 PM
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Update 43/24/2011 10:30:00 PM
Update 33/22/2011 11:15:00 AM  
Update 23/12/2011 11:30:00 PM
Update 13/11/2011 10:15:00 PM  
First Posting 3/11/2011 2:00:00 PM  
Posting Date: 3/11/2011 10:15:00 PM
Friday’s massive M9.1 earthquake—the strongest in Japan’s recorded history—has caused extensive destruction across much of the country’s northeast. It is believed that the quake ruptured three segments of the subduction zone off northern Japan (see map below). The rupture plane is estimated to be some 400 km in length and 200 km wide and the magnitude is the largest in Japan’s historical record, which dates back several centuries. The quake generated a powerful tsunami several meters high in some areas that swept over hundreds of miles of coast, washing away cars, buildings, and boats and inundating croplands. The death toll is currently estimated to exceed one thousand, and hundreds of people remain missing.

Aftershocks continue to shake the region. At least twenty have registered moment magnitudes of 6.0 or more and one measured a magnitude of 7.1. Officials report that thousands of buildings, including approximately 1,800 residential homes in Minami-soma Fukushima prefecture, are destroyed or severely damaged. The Fire and Disaster Management agency reported that the quake has sparked more than 115 fires across the affected region, including extensive fires in Kesennuma in Miyagi prefecture and in Hakodate, a port city on southern Hokkaido Island. Fire-following earthquake damage is typically covered under residential and commercial policies, even in the absence of earthquake-specific coverage.

An irrigation dam in Fukushima failed, washing away scores of homes. More ominously, the government has declared a nuclear emergency at the Fukushima Daiichi nuclear power station after the reactor's cooling system failed. It has been reported that authorities are currently venting radioactive steam and thousands of residents have been evacuated from within six miles of the plant. Meanwhile, a nuclear emergency has been declared at a second power plant where a cooling system had also failed, although it is not clear that there would be a need to release pressure by releasing radiation.

According to the Japan Meteorological Agency (JMA), 17 prefectures experienced seismic intensities of greater than 5 (for a description of intensities, refer to this table on the JMA website).

Based on AIR’s latest detailed industry exposure database for Japan, the Table 1 below lists total insured replacement values (residential, commercial and agricultural buildings and contents) in each of these affected prefectures (see map below for reference). Values are in trillions of Japanese Yen (JPY).

Table 1. Total Replacement Value of Insured Properties by Prefecture (Trillions of JPY).

Figure 1 shows the distribution of insured exposure in Japan, along with seismic intensity by prefecture as reported by the JMA.

Figure 1: Distribution of Insured Residential and Commercial Properties, Rupture Plane and Segments Ruptured.

With respect to the devastating tsunami, official reports indicate that the prefectures of Fukushima, Ibaraki, Iwate and Miyagi were the most severely affected. While waves came ashore both further south and as far north as Hokkaido, information currently available suggests that damage from the tsunami in these areas is not likely to be significant.

To assist in gauging the potential of losses due to tsunami damage, the table below shows estimates of total insured replacement values (residential, commercial and agricultural buildings and their contents) for three distance bands: 0-1 km, 1-2k m and 2-3 km from the coast. The values are from AIR’s detailed industry exposure database for Japan and are in billions of Japanese Yen (JPY). However, there is considerable uncertainty regarding how far inland the tsunami waves penetrated and the distance will vary greatly depending on the orientation of the coastline, bathymetry, elevations and land use-land cover.

Table 2. Total Replacement Value within 0-1 km, 1-2 km and 2-3 km from the Japan Coast, All Lines Combined (Billions JPY).

The AIR earthquake team is analyzing the seismological data for this event as it becomes available and AIR will continue to provide updates as events unfold.

Tohoku Japan Earthquake
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