Japan Aftershocks—M5.7 and M6.9; Insured Losses less than $100 Million USD


Two notable earthquakes occurred in Japan on March 14 both part of the continuing aftershock sequence from the M9.0 Tohoku earthquake of March 11, 2011.

A non-damaging M6.9 earthquake occurred 300 km offshore of the northernmost tip of Honshu. Three hours later and 700 km to the south, a M5.7 earthquake with minor damage potential occurred 90 km east of Tokyo and 30 km east of Narita international airport at a shallow depth of 17 km.

The M6.9 earthquake offshore was perceived lightly throughout northern Honshu and Hokkaido. No damage is expected due to its long distance from populated regions. A tsunami of significance is unlikely from an earthquake of this magnitude, and the Pacific Tsunami Warning Center has not issued a tsunami warning.

The M5.7 earthquake east of Tokyo caused strong shaking felt across the Kanto plain. The Narita airport briefly suspended operations for inspections. EQECAT estimates insured losses less than $100 million USD due to this event.

Narita Aftershocks, March 14, 2012

Narita Aftershocks, March 14, 2012
Source: U.S. Geological Survey (USGS)

In the M5.7 earthquake, a population of approximately 1.5 million was exposed to strong or very strong shaking intensity, according to PAGER estimates. Tokyo experienced light shaking intensity.

No notable damage has yet been reported from the M5.7 earthquake. Likely losses will be characterized by minor damage to contents or architectural components such as ceilings or windows. Isolated instances of structural damage are possible in aging buildings, particularly those of timber construction. A comparable magnitude earthquake in a region less-prepared than Japan may have caused significant damage and human loss.

The EQECAT model for Japan contains 18 events within 10 km and a 0.2-magnitude increment of the M5.7 earthquake.

The best-matched proxies are event IDs 56165 and 56166.

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