Systematic correlations of the earthquake frequency‐magnitude distribution with the deformation and mechanical regimes in the Taiwan orogen

• Published in: Geophysical research letters Vol. 43; no. 10; pp. 5017 - 5025
• Main Authors: Chen, Yen‐Ling, Hung, Shu‐Huei, Jiang, Juen‐Shi, Chiao, Ling‐Yun
• Format: Journal Article
• Language: English
• Published: Washington John Wiley & Sons, Inc 28.05.2016; Wiley
• Subjects: Brittleness; brittle‐plastic transition; Correlation; Crustal deformation; Deformation; Deformation mechanisms; Depth; Distribution; Ductile brittle transition; earthquake frequency‐magnitude distribution; Earthquakes; Faults; Fracture mechanics; Geological faults; Mountains; Orogeny; Plastics; Seismic activity; Seismicity; Slip; Stress concentration; Stresses; stress‐dependent b value; Strikes; Taiwan orogen; Thrust; Yields; ISEW, Taiwan
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1002/2016GL069020

We investigate the correlation of the earthquake frequency‐magnitude distribution with the style of faulting and stress in Taiwan. The b values estimated for three types of focal mechanisms show significant differences with the lowest for thrust, intermediate for strike slip, and highest value for normal events, consistent with those found in global and other regional seismicity. Lateral distribution of the b values shows a good correlation with the predominant faulting mechanism, crustal deformation, and stress patterns. The two N‐S striking thrust zones in western and eastern Taiwan under the larger E‐W shortening and differential stress yield the lower b values than those in the in‐between mountain ranges subject to the smaller extensional stress and dominated by strike slip and normal faults. The termination of the monotonically decreasing b value with depth at ~15–20 km corroborates its inverse relationship with stress and the existence of the brittle‐plastic transition in the weak middle crust beneath the Taiwan orogen. Key Points General dependence of the b value with the style of faulting and stress is first verified in the Taiwan orogen Regional b value variations correlate well with the crustal deformation and stress regimes manifested from the local tectonics The depth‐varying b value reveals the brittle‐plastic transition at ~15–20 km and a weak middle crust under Taiwan