DISTRIBUTION OF STRAIN RATES IN TAIWAN BEFORE AND AFTER 1999 CHI-CHI EARTHQUAKE AND THEIR GEODYNAMIC MECHANISMS
Zhu Shoubiao 1) ; Zhao Xiaoyan 2) ; Liu Yang 3) ; and Miao Miao 3)
1)State Key Laboratory of Earthquqke Dynamics,Institute of Geology,CEA,Beijing 1000292)College of Disaster Prevention Techniques,Sanhe 0652013)Institute of Crustal Dynamics, CEA,Beijing 100085
Abstract：The destructive ChiChi earthquake occurred in 1999, which had a full impact on the stress state in Taiwan. The strain rates based on the GPS data before and after the 1999 ChiChi earthquake in the period of 1990-1995 and of 2003-2005 were estimated respectively. The computed results show that the pattern of strain rate distribution in Taiwan is not changed much before and after the ChiChi earthquake. The highest value of the maximum principle strain rates is located on the Coastal Range, which orientated obliquely to the trend of Taiwan. Deceasing rapidly from east to west, the values of principle compressive strain rates are less than those of extensive strain rates on the Central Range, behaving on tensile strain state there. And principle compressive strain rates are very small on the western Coastal Plain. At the same time, the orientations of principle strain rates are agreement with those of Pand Taxis in focal mechanisms in Taiwan. The high value of the maximum shear strain rates is located on the Coastal Range where the surface dilatation rates are negative, and the absolute value is highest in Taiwan. However surface dilatation rates are positive on both the northern and southern sides of the Central Range. The computed results demonstrate that the Coastal Range is the central collision zone between Taiwan and Luzon arc, and material escapes toward two directions of NE and SW, respectively. In the period of 2003-2005, after 4 years since the ChiChi earthquake, the maximum shear strain rates become much larger than those in the period of time before the mainshock which may be resulted from the changes of the physical properties of the medium in focal regions, also suggesting that the medium did not resume to the state before the ChiChi earthquake,yet.
Zhu Shoubiao ,Zhao Xiaoyan ,Liu Yang et al. DISTRIBUTION OF STRAIN RATES IN TAIWAN BEFORE AND AFTER 1999 CHI-CHI EARTHQUAKE AND THEIR GEODYNAMIC MECHANISMS[J]. jgg, 2011, 31(2): 38-43.
