Precise Temperature Measurements and Earthquake Heat Associated with the 1999 Chi-Chi, Taiwan Earthquake

Abstract

% to 90%) of the total to 90%) of the total seismic energy budget, and geophysicists have long discussed the level of heat that should be observable (Brune et al., 1969; Lachenbruch and Sass, 1980; Scholz, 2002; Terada, 1930). Precise temperature measurements across the fault immediately after an earthquake can provide the most unambiguous answer; however, there has never been a ; however, there has never been a however, there has never been a however, there has never been a owever, there has never been a significant near-fault temperature change observed for any previous large earthquake that can be attributed to the frictional heating. This is because there has been no appropriate site for temperature measurements around a fault at depth just after an earthquake. The most promising way to reach the fault zone in order to observe the frictional heat is to drill a borehole to the area where large slip occurs. There have been several drilling projects to reach deep areas of the fault zone, such as the Taiwan Chelungpu fault Drilling Project (TCDP), San Andreas Fault Observatory at Depth (SAFOD), and the planned NanTroSEIZE project. We , and the planned NanTroSEIZE project. We and the planned NanTroSEIZE project. We reported the first successful temperature measurement of deep fault zone boreholes that was drilled by TCDP at the Chelungpu fault, Taiwan (Kano et al., 2006). An observation of a temperature increase, and thus an estimate of the heat generated, provides information about the frictional strength during faulting and the level of driving stress for an earthquake. These are key unknown values of important parameters that are necessary for understanding the physical process of earthquake ruptures. In this paper we outline the results of the precise temperature measurement in TCDP Hole A as an attempt to directly A as an attempt to directly A as an attempt to directly measure the frictional heat produced by an earthquake. an earthquake.