Satoko Oki

Public anxiety after the 2011 Tohoku earthquake: fluctuations in hazard perception after catastrophe

In 2011, Japan received a massive blow from the Tohoku Earthquake and the ensuing disaster at the Fukushima Dai-ichi Nuclear Power Generation Plant (hereafter, the Fukushima Nuclear Plant), with 18,000 people dead or missing, and more than 330,000 evacuated long-term. Anxiety among the people of Japan concerning earthquakes and nuclear accidents is higher than ever, but other hazards confront them as well. This research investigated whether the Japanese people’s anxiety about a variety of other hazards has increased or decreased since the Tohoku Earthquake. Based on the availability heuristic, the contrast effect, and the finite-pool-of-worry hypothesis, it was predicted that public anxiety about earthquakes and nuclear accidents would increase, but anxiety about other hazards would decrease. Data from two nationwide surveys conducted in January 2008 and January 2012 were compared to see the change in societal levels of anxiety toward 51 types of hazards. The results showed that anxiety had increased after the Tohoku Earthquake for only one hazard other than earthquakes and nuclear accidents. For 29 other hazards, the anxiety levels had significantly decreased; and for the remaining 19 hazards, there was no significant change. These results support the prediction, indicating that post-disaster, the overall anxiety levels of the Japanese people tended to decline. Practical implications were discussed with a focus on problems that might be caused by the changes in anxiety level.

Joint inversion of teleseismic and InSAR datasets for the rupture process of the 2010 Yushu, China, earthquake

We have examined the rupture process of the 2010 Yushu, China, earthquake, which occurred in the eastern Tibetan plateau. Based on the results of centroid location grid searches, the aftershock distribution, and InSAR observations, we first constructed a left-lateral strike-slip bending fault model. We then carried out joint inversions of the teleseismic waveform data and InSAR data using various rupture front velocities. We obtained the optimum source model with a seismic moment of 2.3 × 1019 N m (Mw ∼ 6.8), where the rupture velocity was found to be slightly faster than the shear wave velocity of the crust in this region. This supershear rupture velocity resulted in severe damage in and around the county seat of Yushu, which is located in the forward rupture direction of the source model. The features of this event, such as the shallow and fast rupture propagation may represent a seismic feature of the tectonic activity in the eastern Tibetan plateau.