東海地震のアスペリティの推定 : 東海地域の地震活動変化と地殻変動 : その5 Presumption of Asperities for the Anticipated Tokai Earthquake : Seismic Activity Change and Crustal Deformation in the Tokai Region : Part 5
It is meaningful to presume the location of asperities for the anticipated Tokai earthquake in view of risk assessment and also for earthquake prediction. These asperities were first specified based on the seismic activity change, and verified in comparison with the result derived from GPS measurements. In central Shizuoka Prefecture, the seismicity change progressed almost simultaneously with the slow-slip beneath Lake Hamana from 2000 to 2005 and resulted in a separation of the activity into quiescence and activation. This change was considered to be caused by a quasi-static slip on the locked plate boundary, triggered by the slow-slip, and the activated zones were assigned to be asperities due to stress concentration there. We thus extracted several zones as candidates of the major asperities. On the other hand, the Japanese University Consortium developed a dense GPS network in the western and central parts of Shizuoka Prefecture in order to know the crustal deformation in detail. Analyzing the data together with those from GEONET by the Geographical Survey Institute during two years since 2004, we got the detailed distribution of the areal strain associated with the slow-slip. The results show a patch-like pattern between the contracted areas and the dilated ones with a wavelength of about 20 km. We estimated areal strain by using a dislocation model arranged for the candidates of the asperities obtained from the seismicity change, and compared it with that from the GPS measurements. The result gave a good correspondence between them. This fact suggests that the presumed asperity model is reliable and valuable in the study on hazard mitigation against the anticipated Tokai earthquake.
- 地震. 2輯
地震. 2輯 60(4), 267-277, 2008-03-31
SEISMOLOGICAL SOCIETY OF JAPAN