Science Links Japan | Relationship between Distributions of Shallow Earthquakes and Gradients of Gravity Anomaly Field in Southwest Japan.

Relationship between Distributions of Shallow Earthquakes and Gradients of Gravity Anomaly Field in Southwest Japan.

Accession number;00A0320339

Title;Relationship between Distributions of Shallow Earthquakes and Gradients of Gravity Anomaly Field in Southwest Japan.

Author; KUDO TAKESHI (Riken Inst. of Phys. and Chem. Res.) KONO YOSHITERU (Fac. of Sci., Kanazawa Univ.)

Journal Title;Journal of the Seismological Society of Japan. Second Series

Journal Code:G0931A

ISSN:0037-1114

VOL.52;NO.3;PAGE.341-350(1999)

Figure&Table&Reference;FIG.10, REF.17

Pub. Country;Japan

Language;Japanese

Abstract;Relationship between distributions of shallow earthquakes and gradients of gravity anomaly field in Southwest Japan is investigated. Zones with steep horizontal gradient of gravity anomaly field are presumably caused by faults bounding different density structures in the crust. On the other hand, most shallow earthquakes are supposed to be caused by dislocations at faults in the crust. From both presumptions, it follows that the distribution of epicenters should be overlapped with that of the steep gravity gradient zones. This study verified the overlap in Southwest Japan. However, very low seismicity along the steep gradient zone of gravity anomaly was followed by the mainshock of the 1995 Hyogo-ken Nanbu earthquake (the Kobe earthquake). We also assessed such kind of seismic gaps beneath the steep gradient zones of gravity anomaly field. Many steep gradient zones of gravity anomalies with very low seismicities can be extracted. Some of them might be due to density contrasts at geological boundaries or inactive faults and some can be areas of future seismic hazards like the case of the Kobe earthquake. (author abst.)

Related Articles;