Abstract
Using the empirical attenuation relationship between the maximum acceleration and source distance, we evaluated the amplitude level of the strong ground motion which might be possible at stations of the DONET (Dense Ocean-floor Network System for Earthquakes and Tsunamis), deployed in the source area of the Tonankai earthquake. We firstly studied on how often the maximum acceleration data exceeds the criteria, such as 1g, 2g, 3g, and 4g, using the maximum acceleration data from recent fourteen off-shore earthquakes of magnitude around 7 or more and 2008 Iwate-Miyagi Inland earthquake (Mw6.9). We modified the maximum accelerations by compensating the attenuation effect, so as to derive the distributions of the corrected acceleration values which might be observed at an epicentral area. Next, we evaluated the exceeding probabilities of such criteria at the DONET stations against the 1944 Tonankai earthquake (Mw8.1). After selecting five reference events who involved the maximum acceleration data larger than 3g after such correction, we obtained the distribution of the ratio between the data and the prediction and evaluated the exceeding probabilities for above criteria. Through the study, it is clarified that the upper limit of the maximum measurable acceleration of the DONET should be 4g, to avoid saturation by the extremely strong ground shaking from nearby source rupturing as much as possible.
