観測記録に基づいたスラブ内地震の短周期レベル

概要

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Acceleration source spectra of three intra-slab earthquakes which occurred recently were evaluated by eliminating the effects of propagation path and site characteristics from observation records. Short-period spectral level A were evaluated from the acceleration source spectra, and stress parameters Ao were calculated from A and seismic moment M0. The relationship between Ao, focal mechanism, regionality, location, M0, and focal depth were examined. Ao of intra-slab earthquakes was not much affected by focal mechanism, regionality in the Pacific plate. The effect of location and focal depth to Ao is not clear, but Ao is not dependent on focal depth for medium and large earthquakes in the Pacific plate. Upper level of Ao is not affected by M0 and is 40-80 MPa. But lower level of Ao is affected by M0, that is, lower than 5 MPa for small earthquakes（M0＜5 ×1017 Nm）, 20- 80 MPa for medium earthquakes（5 ×1017 Nm＜M0＜1×1019 Nm）, and 60-80 MPa for large earthquakes（ M0＞1 ×1019 Nm）.
2010-03-19