The study of fracture energy in TCDP Hole-A
Date Issued
2008
Date
2008
Author(s)
Yu, Ai-Chi
Abstract
Slip-weakening model can be used to explain the relationship between energy budget and physical processes of earthquake slip. Based on the model, the elastic strain energy released during an earthquake is partitioned into the fracture energy (EG), frictional heat (EH), and radiation energy (ER). Although radiation energy and fracture energy only occupy the small portion of total elastic energy, their ratio is the main factor of controlling earthquake rupture dynamics, expressed by radiation efficiency ηR = ER / (ER + EG). Fracture energy is defined as the energy at rupture tips that is required to create a rupture surface and produce a breakdown in strength.t is common to observe the grain-size reduction associated with the development of fault gouge within seismogenic faults. Also, the major displacement along mature faults usually occurred within the fault gouge. Thus, by estimating the fracture energy from the grain size distribution of fault gouge of TCDP cores, it can provide insights into understanding of faulting dynamics of the Chi-Chi earthquake. TCDP retrieved cores from two holes around the Dakeng area in 2004-2005. From the hole-A core, the Chelungpu fault zone, which slipped during the Chi-Chi earthquake, occurs at 1111 m depth, consisting of a 1-m-thick fault core including 12-cm-thick primary slip zone and several meters thick of damaged zone. Above the fault, there are many small faults can also be observed. The fault gouge of these small faults is only several millimeters to several centimeters thick, and the damaged zone does not develop well. We analysed the grain size distribution of the small faults and the primary slip zone of Chelungpu fault using particle size analyser and microscope measurements, to estimate the fracture energy associated with the gouge development.he fracture energy per millimeter thick gouge of small faults ranges from 2.76E+04 to 4.95E+04 Jm-2 and is smaller than fracture energy per millimeter thick gouge of the primary slip zone of Chelungpu fault which ranges from 1.03E+05 to 1.44E+05 Jm-2. This difference could be explained by that underestimation of small grain size portion and/or experimental error from particle size analyser measurement or that these small faults are products of creeping. After estimating the total fracture energy of the primary slip zone of Chelungpu fault (7.78E+05 to 2.12E+06 Jm-2), we can calculate the fracture energy associated to a single earthquake.
Subjects
Chelungpu fault
fracture energy
fault gouge
grain size distribution
Type
thesis
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