Large, frequent earthquakes delay restoration in Japan
Earthquakes and aftershocks are continuing to affect Japan, even weeks after the Magnitude 9.0 Tohokku-oki earthquake on March 11.
EQECAT says ground motions from these events have been less severe and more geographically compact than the motions from the March 11 event but the continued earthquake activity is contributing to delayed restoration of economic and social activities in the region, potentially impacting insured losses for business interruption and contingent business interruption, although these effects are not quantifiable at this time.
The aftershock sequence of the Tohoku-oki earthquake will most likely persist for at least a year and probably longer, said EQECAT. The aftershock activity will decrease with time at an exponential rate, but the magnitudes of the sequence will be randomly distributed during that time. According to the USGS, a rule-of-thumb used by seismologists is that the largest aftershock will most likely have a magnitude one unit lower than the mainshock. In this case, that would allow for an aftershock up to M 8. Note that an M 7.9 aftershock occurred on the same day as the mainshock. However, it is not clear that this will be the largest aftershock to occur in the entire sequence.
The continued seismic activity is expected to inhibit the restoration of activities in Northern Honshu. In addition to the disruptions caused by the earthquake aftershocks (earthquakes cause pre-cautionary halts to train services; require inspection of bridges; and small-scale power outages), exacerbating factors unique to this event include:
- A level 7 nuclear spill incident at the Fukushima Daiichi nuclear power plant requiring implementation of “planned and extended” counter measures. The evacuated areas are not expected to be re-inhabited in the near-term future, forcing the re-location of residents and all commercial activities, including access to port facilities.
- Disrupted roads, railways, and port facilities. Difficult to reach even before March 11, the disruption of these key infrastructure components are slowing the restoration of activities to a ‘normal’ state.
- Electrical shortages are expected to persist for a while, as two nuclear power plants are significantly damaged, and two more were impacted by this earthquake. With four of 55 nuclear power plants in the country impacted, shortages of electric power will disrupt a very broad cross-section of Japan, extending beyond the Miyagi coast line.
- Petroleum refining and storage – about 5% of the country-wide refining capacity was in the two refineries most impacted by this event – Cosmo Oil in Chiba (fire) and the Sendai refinery. This should not significantly impact the access to transportation fuels in the country, although regional impacts in Miyagi are expected.
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