Case 2: Foreshocks to the Haicheng Earthquake of 1975. Certain Characteristics of the Haicheng Earthquake (M=7.3) Sequence
- Max Wyss
Published Online: 3 APR 2013
Copyright 1991 American Geophysical Union.
Evaluation of Proposed Earthquake Precursors
How to Cite
Wu, K.-T., Yue, M.-S., Wu, H.-Y., Chao, S.-L., Chen, H.-T., Huang, W.-Q., Tien, K.-Y. and Lu, S.-D. (2013) Case 2: Foreshocks to the Haicheng Earthquake of 1975. Certain Characteristics of the Haicheng Earthquake (M=7.3) Sequence, in Evaluation of Proposed Earthquake Precursors (ed M. Wyss), American Geophysical Union, Washington, D. C.. doi: 10.1029/SP032p0012
- Published Online: 3 APR 2013
- Published Print: 1 JAN 1991
Print ISBN: 9780875907840
Online ISBN: 9781118667873
- Earthquake prediction—Evaluation
This paper deals with the seismicity (the earthquake sequence and its spatial distribution) related to the Haicheng earthquake of February 4, 1975.
Normally, very low seismic activity existed around the meizoseismal region of the Haicheng earthquake. However, beginning February 1, 1975, 527 foreshocks were counted at the Shipengyu seismograph station located about 20 km from the epicenters. The epicenters of these foreshocks were densely concentrated, and the sense of the P-wave first motions was similar. With respect to the time of occurrence, the succession consisted of a concentration of foreshocks followed by a period of quiescence and finally the main shock. Following the main shock, numerous aftershocks occurred.
The direction of the major axis of the meizoseismal region of the main shock coincides with both that of the aftershock distribution and the direction of the nodal plane A, from the earthquake fault plane solution. From this the strike of the dislocation plane of the main shock was interpreted to be WNW. The fault appears to be left lateral strike-slip with a high angle of dip.
Some discussion is also given to a possible method of imminent earthquake prediction.