Based on early calculations and modeling conducted by
In its calculations, AIR simulated dozens of scenarios with varying magnitude (8.9 to 9.1), focal depth (9 miles to 18 miles) and rupture width (62 miles to 93 miles). The losses are most sensitive to rupture dimensions, and become extremely large if the modeled rupture is extended southward toward the Tokyo and Chiba prefectures, which contain a higher concentration of insured properties.
According to AIR, earthquake insurance penetration in Japan is relatively low (ranging between 14% to 17% nationwide). About 70% of all residential construction is estimated to be of wood and about 25% of concrete. Commercial construction consists of more than 50% concrete, about one-third light metal or steel, and less than 10% wood. Residential structures in the region of Japan impacted by today’s quake are generally resistant to earthquake shaking. Some vulnerable structures do exist; they are comprised of non-ductile reinforced concrete frame and heavy wood-frame construction.
AIR’s calculations take into account insured physical damage to property (residential, commercial/ industrial, and agriculture), both structures and their contents resulting from shake and fire following; and direct business interruption losses.
However, considerable uncertainty still remains in the modeling firm’s ability to create a more extensive damage assessment. In particular, the website of Japan’s national seismic network remains offline, so ground motion observations are still unavailable. In a statement, AIR said it considers this a preliminary loss estimate and plans to refine it when additional information such as ground motion recordings becomes available.
“Given the enormity of the Mw9.1 earthquake that struck Japan two days ago, it is still in the very early aftermath of the event,” said Dr. Jayanta Guin, SVP of research and modeling at AIR Worldwide.
Additionally, the AIR Earthquake Model for Japan does not account for the effects of tsunami. As more detailed information becomes available, AIR plans to independently estimate the loss due to tsunami and provide a combined loss estimate that avoids double-counting in the affected areas.
The event is the largest in Japan’s lengthy earthquake history, with the rupture extending across four segments of the subduction zone that parallels the Japan coast to the east. Seismologists both inside and outside Japan have said that such a scenario had not been contemplated and it was therefore not included in the official national seismic hazard maps of Japan.
A major area of concern yet to be determined is the aftereffects of the crippled Fukushima Daiichi Nuclear Power Station. An explosion in one of the buildings prompted officials to expand the evacuation area around the plant to a 12-mile radius, affecting as many as 170,000 people. Initial reports indicated that leaks of radioactive materials, which had begun immediately after the explosion, had diminished. Most recently officials have now flooded the reactor with seawater in an effort to avoid a nuclear meltdown. The seawater is likely to permanently disable the reactor. On Sunday morning, local time, a second reactor at the same plant was also experiencing critical failures of its cooling system.
The tsunami remains the main story of this event as it will be responsible for most of the fatalities. The JMA has reported maximum tsunami heights of three meters or more for the northeast coast of Japan, with the prefectures of Fukushima, Ibaraki, Iwate and Miyagi being the most severely affected. In Miyagi prefecture, some waves reached 6 miles inland. AIR plans to use this and other information as it becomes available to estimate the loss resulting from the tsunami and to issue a combined shake, fire-following and tsunami loss estimate.
