Preliminary analysis on the tectonic stress level in the source region of Tangshan earthquake

Introduction Analyzing tectonic stress field based on focal mechanism data is an important way to the study tectonic evolvement of lithosphere and associated dynamic process. Such studies growrapidly in China and abroad (Zoback, 1992; Plenefisch, Bonjer, 1997; XU, 1985; CUI, XIE, 1999). At present most of the studies focus on the inversion of focal mechanism data for the direction and relative magnitude of stress tensor, and few on absolute stress. Using focal mechanism and fault scratch,…

Preliminary analysis on the tectonic stress level in the source region of Tangshan earthquake

The abundant data of focal mechanism solutions in Tangshan region, China, are inverted for the tectonic stress field. Combined with tectonophysical consideration, the magnitude of the three principal stresses, as well as their vertical variation under the average crustal rock property, in the source region of the 1976 Tangshan earthquake is estimated. The relationship between crustal stress and friction mc, pore pressure P0 and stress shape factor F is studied. The paper draws the conclusion that the vertical increasing rate of the maximum principal stress s is directly proportional to friction, and inversely to pore pressure P0 and stress shape factor F ; while the vertical increasing rate of the minimum principal tress s is directly proportional to pore pressure P0, inversely to friction mc and stress shape factor F. This study is a try to invert the data of focal mechanism solutions for the complete stress tensor.