Granite deformation and behavior of acoustic emission sequence under the temperature and pressure condition at different crust depths |
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| Authors: | JIANG Hai-kun Zhang Liu ZHOU Yong-sheng |
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| Institution: | (1) Institute of Geology, China Seismological Bureau, 100029 Beijing, China;(2) Opening Laboratory of Tectonophysics, China Seismological Bureau, 100029 Beijing, China |
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| Abstract: | Results of triaxial compression experiment results show that granite rock strength increases with the depth until 30 km. In
shallow crust, rock failure exhibits abrupt or quasi-abrupt instability under lower pressure. Acoustic Emission (AE for short)
distributed almost uniformly before and after failure. Go through downwards into the depth range with progressive failure
feature, there are no or only a few number of AE before and after failure. In deeper range, rock failure shows some feature
of quasi-abrupt instability under high pressure. There are still few AE before failure, but with the stick-slip, much more
AE events were detected after failure. Under the temperature and pressure condition of more deep crust (about 26 km), rock
failure takes abrupt instability under high pressure as main feature, there are dense AE activities before failure and cumulated
frequency of AE increases exponentially before the failure. In about 35 km depth range, rock strength decreases quickly with
the depth and sample exhibits semi-ductile or ductile progressive fails, there are no AE being detected before and after failure.
The b value of AE sequence before failure seems a little smaller than that after failure, and b value roughly decreased with depth. The numerical range of index α is the widest in about 18 km depth and becomes narrow
in the condition of more shallow or more deep crust. So, when the temperature and pressure condition simulating the real environment
of focal depth changes from shallow to deep in the crust, the range of α of microfracture sequence would undergo such an evolvement
process that α changes from narrow to wide and then to narrow again.
Foundation item: Project 95-04-02-01 from CSB and Project Y97E02079 from the Natural Foundation of Shandong Province. The experiment works
were also supported by the fund of Laboratory of Tectonophysics, CSB
Contribution No. 2000B0012, Institute of Geology, China Seismological Bureau. |
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| Keywords: | high temperature and high pressure granite deformation and failure acoustic emission local scale index spectra |
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