著者

Toshihiko HASHIDA Kunihiko SHIMAZAKI

出版者

The Seismological Society of Japan, The Volcanological Society of Japan , The Geodetic Society of Japan

雑誌

Journal of Physics of the Earth (ISSN:00223743)

巻号頁・発行日

vol.32, no.4, pp.299-316, 1984 (Released:2009-04-30)

参考文献数

21

被引用文献数

18 21 31

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Seismic intensity data, which measure the degree of ground shaking, contain information on attenuation along the path from the source to the station and earthquake source strength. With some reasonable assumptions about the seismic intensity data, a properly formulated damped least squares estimation procedure can be used to determine simultaneously both three-dimensional attenuation structure and source strength. By means of this method, sufficiently distributed earthquakes with a large amount of seismic intensity data may provide information on the crust and upper mantle Q structure in a region where a spatial variation of attenuation is large enough to affect the distribution of seismic intensity. To check the validity of the method, numerical experiments were undertaken for artificial data including errors comparable to those expected from using seismic intensity. The results obtained for a two-dimensional island arc structure model show the method to be practical. The reliability of the obtained solution for Q structure can be measured by the corresponding diagonal element of the resolution matrix. By using a large number of seismic intensity data up to about one thousand and selecting solutions with high resolution, a Q structure with an accuracy of 1.5×10-3 in 1/Q and a source strength with an accuracy of 0.1 in magnitude scale can be obtained. This method is extendable to many regions including island arcs and continents because large amounts of intensity data are easily attainable.

著者

Toshihiko HASHIDA Kunihiko SHIMAZAKI

出版者

The Seismological Society of Japan, The Volcanological Society of Japan, The Geodetic Society of Japan

雑誌

Journal of Physics of the Earth (ISSN:00223743)

巻号頁・発行日

vol.35, no.5, pp.367-379, 1987 (Released:2009-04-30)

参考文献数

16

被引用文献数

2 3

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Predictions of seismic intensities are attempted based on a three-dimensional attenuation structure and amplifying factors at stations obtained in the previous study for the Tohoku district, Japan. An empirical relation between `earthquake size' related to the intensity and JMA magnitude MJ is also used. The first prediction is to map spatial distribution of the minimum magnitude MJ of an earthquake which causes intensity 5 at a specific JMA station. The result shows that the effects of regional variation of attenuation and local site condition at the station are important in assessing the seismic hazard. Another attempt is made to predict an annual number of felt earthquakes at each JMA station based on the JMA earthquake catalogue for a period from 1963 to 1984. A comparison of predicted number with the observed one shows a good coincidence between them for each year. This may suggest that the proposed method can successfully predict intensities. However, a comparison of the predicted cumulative number for each intensity grade with the observed one shows that the cumulative numbers for intensities 2, 3, and 4 are underestimated by the proposed method. This result may suggest a nonlinearity between the JMA intensity scale and the logarithm of acceleration, which has been suggested by other evidences.