HR: 0800h
AN: S21B-0564    [Abstracts]
TI: Thermal Field Indicator for Identifying Active Faults and its Instability From Laboratory Experiments
AU: * Ma, J
EM: majin@ies.ac.cn
AF: State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Postbox 9803, Beijing, 100029, China
AU: Liu, L
EM: liulq48@hotmail.com
AF: State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Postbox 9803, Beijing, 100029, China
AU: Liu, P
EM: liupeixun@sina.com
AF: State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Postbox 9803, Beijing, 100029, China
AU: Ma, S
EM: masp@bit.edu.cn
AF: Beijing Institute of Technology, Beijing Institute of Technology, Beijing, 100081, China
AB: The relationship between the thermal filed and strain field during deformation of faults is the physical basis to clarify whether satellite infrared information and the ground temperature field can be used to study fault activity. This study attempts to discuss these problems by experiments in the laboratory. The two-direction servo-control system was used to load on the samples with compressional and extensional en echelon faults. An infrared thermal image system and a contact-type thermometer recorded synchronously variations of the bright temperature field of infrared radiation and temperature field during deformation of the rock specimens. A digital CCD camera and a soft ware based on the digital speckle correlation method (DSCM) was utilized to capture images and to analyze them, yielding processes of displacement and strain fields. The experimental result shows as follows: 1 The temperature is highest at the jog area of the compressional en echelon faults, whereas that is lowest at the extensional en echelon faults prior to failure of the jog area. The record by DSCM displays that the mean strain of the jog area is largest for the compressional en echelon faults, while that is smallest for the extensional en echelon faults. These mean that the temperature field has clear responses to the opposite stress states at the jog areas of two kinds of en echelon faults, providing an indicator for determining whether the fault segment has slid. 2 The en echelon faults experience two deformation stages from stress building up and fault propagating at the jog area to unstable sliding along the fault. Correspondingly the mechanism of heating-up is turned from strain heating into frictional heating. Three kinds of phenomena have been observed at the jog area and its vicinity during the stage of transformation. They are temperature drop, fast fluctuation of temperature, and pulses of temperature rising, respectively. Mechanism of these phenomena is discussed. 3 These variations of the thermal field at the jog area are followed by swift rise of temperature along the fault. The onset of temperature rise along fault occurs 2-3 seconds prior to its unstable slip. However, the temperature drop of the jog area happens about 20 seconds before the unstable slip of the fault and the appearance of temperature rising pulses is 10-20 seconds earlier than that of the unstable slip. They are precursors to unstable slip of the fault. These experimental analyses demonstrate that observations and studies on the thermal variations at the sensitive portion of a faults comparing with other relevant data are of great importance for detecting precursors ahead of unstable slip of active fault.
DE: 7209 Earthquake dynamics (1242)
DE: 7223 Earthquake interaction, forecasting, and prediction (1217, 1242)
DE: 7260 Theory
DE: 8040 Remote sensing
DE: 8123 Dynamics: seismotectonics
SC: Seismology [S]
MN: 2007 Fall Meeting