Significant damage not expected from Japanese earthquake: RMS

by Artemis on November 22, 2016

The major earthquake that struck off the coast of Japan in the early hours of this morning local time and the tsunami waves that followed, are not anticipated to have caused significant damage, according to risk modelling firm RMS.

Japan earthquakeThe earthquake which was preliminarily reported as a magnitude 7. but later downgraded to a magnitude 6.9 caused evacuations in many coastal regions of Fukushima and surrounding prefectures in Japan, as memories of the terrible toll from the 2011 Tohoku earthquake returned.

However the USGS said that there is only a 4% chance of economic losses rising above $10 million, which while it seems low reflects the fact that the quake was offshore.

The earthquake caused tsunami waves for some hours following the event, with tsunami waves recorded as high as 1.4m. Japan’s sea defenses are largely able to contain these smaller waves however and damage is said to have been slight.

The insurance and reinsurance industry will have been watching the event unfold closely, as initial warnings suggested that tsunami heights could have reached 3 meters. But thankfully the waves were much lower and impacts on land from ground shaking have also been much fewer than anticipated.

The ground shaking from the quake did impact one of the nuclear plants, the Fukushima Daini installation, where a cooling system for a spent nuclear fuel pool was knocked offline. However TEPCO brought the cooling system back on line within a couple of hours of the event.

It looks like the earthquake will be a minimal event for the insurance and reinsurance industry, with any insured losses retained largely within the local domestic market and perhaps no impact to reinsurance capital at all.

RMS said that preliminary reports suggest no significant damage has been caused by either the earthquake or the subsequent tsunami waves.

The full report from RMS can be found below.

Dr Robert Muir-Wood, RMS chief research officer, said:

“The 06:00 local time earthquake (November 22) 40km off the coast of Sendai, Japan is thought to have been another aftershock in the long running sequence triggered by the giant Mw9 Tohoku earthquake (March 2011) along the Pacific coast subduction zone plate boundary.

Today’s event (issued at a magnitude between Mw6.9 and 7.4) occurred in the Japanese plate above the southern extent of that 2011 major fault rupture. In this region the 2011 earthquake is not considered to have fully relieved the plate movement on the underlying mega-fault. So some experts in tectonics believe another giant earthquake, greater than Mw8, is still due on the southern continuation of the plate boundary, offshore from the Pacific coast east of Tokyo.

Although today’s earthquake was relatively modest, the Japanese authorities were justified in issuing a tsunami warning even though there is a direct relationship between the magnitude of a shallow earthquake and the size of a tsunami. This warning led people to evacuate from the low lying areas.

Whilst this cautious approach is understandable given the deaths and damage caused five years ago, generally issuing alerts and warnings that trigger evacuations for smaller earthquakes and tsunamis carries the risk that some people may chose not to evacuate quickly enough or at all for future tsunami alerts. One reason people did not evacuate along the coast of Japan in March 2011 was because a previous tsunami warning (after an earthquake in 2006) had proven unnecessary.”

RMS Event Response Team commentary:

  • At 20:59 UTC on Monday November 21 (05:59 local time on Tuesday November 22), an earthquake of Mj7.3, equivalent to Mw6.8, struck approximately 23 miles (37 km) east-southeast of Namie, Japan (pop. ~18,000) offshore at a depth of approximately 7 miles (11 km)
  • The Japanese Meteorological Agency (JMA) is in close agreement with the United States Geological Survey (USGS) which reports a magnitude of Mw6.9
  • Preliminary damage reports indicate that the earthquake and resulting tsunami have not caused any significant damage
  • The JMA has reported that the earthquake is likely to be an aftershock of the Mw9.0 earthquake which occurred in March 2011 near Tohoku. The JMA has warned that another large earthquake could be expected within the next few days
  • Ground shaking was reported across eastern portions of Honshu Island, with Fukushima Prefecture reporting the strongest shaking. The USGS reports a maximum ground shaking of VI (Strong) on the Modified Mercalli Intensity (MMI) scale, which was felt by approximately 222,000 people, with a further 2.4 million people experiencing ground shaking of MMI V (Moderate). Shaking was felt as far away as Tokyo (pop. ~13.6mn), approximately 150 mi (240 km) south-southwest of the USGS epicenter
  • The earthquake generated a tsunami of up to 4.5 ft (1.4m) in height at Sendai Port, approximately 45 miles (70 km) north of Fukushima, with wave heights of up to 2 ft (60 cm) recorded elsewhere along the northeast coast of Japan. As of 09:00 UTC on Tuesday November 22, all tsunami warnings have been cancelled, though residents are advised to avoid the coastline
  • According to local media reports, TEPCO’s Fukushima-Daiichi No. 3 power plant, which is currently being decommissioned, experienced cooling issues during the earthquake which led to the plant closing temporarily. There are no reports of structural damage and the plant is now open. Media reports also indicate that there were no irregularities at the Onagawa or Tokai Daini nuclear power plants
  • Some factories and businesses in Fukushima Prefecture were temporarily suspended during the earthquake, though most have reopened since the tsunami warning was cancelled

Earthquake Parameters

  • According to the USGS, the population in this region resides in structures that are resistant to earthquake shaking, though some vulnerable structures exist
  • The USGS reports that recent earthquakes in this area have caused secondary hazards such as landslides and fires that might contribute to losses
  • Japan is located at the juncture of the Eurasian, North American, Pacific and Philippine Sea tectonic plates. The Pacific Plate subducts beneath the North American Plate at a rate of approximately 83-90 mm/yr. Earthquakes can be generated as a result of interplate slip along the subducting plate interfaces

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