ESR/ICP-MS dating method of the latest fault movement

First，we inspected the resetting state of ESR signals using the Nojima Fault 500米drilling core samples，and confirmed that ESR signals in the fault gouge had been thermally reduced.This means that fault gouge samples as deep as possible are necessary for complete resetting of ESR signals.As a result of computer simulation on the decay process of ESR signals in the fault gouge，it was found that we should consider as a resetting mechanism not only frictional heat but also vaporization or convection of pore and crystal water in the fault gouge.Next，we carried out chemical analysis of the fault gouge in the 500m csamples to confirm whether or not Pb anomaly actually exists.We analyzed by ICP-MS8-20µm fractions separated from the bulk samples of the fault gouge.As a result we detected extreme I D 1208 I D 1 Pb/I D 1232 I D 1 Th and I D 1206 I D 1 Pb/I D 1238 I D 1 U ratio anomalies from the 0-3毫米part just on the fault plane.In the 0-3 mm and 3-6 mm parts of the fault gouge，the intensity of I D 1206文件D 1 Pb/I D 1238文件D 1 U ratio is larger than that of I D 1208文件D 1 Pb/I D 1232文件D 1 Th ratio，whereas in the parts of more than 6 mm away from the fault plane，the intensity of I D 1206文件D 1 Pb/I D 1238 E D 1 U ratio is smaller than that of I D 1 208 I D 1 Pb/I D 1232This suggests that the Pb anomaly may not be derived from the migration of the whole Pb isotopes，but from that of apart of I D 1206 I D 1 Pb or I D 1208锡D 1 Pb.The Pb anomaly may be explained by the existence of Rn anomaly.Furthermore we experimentally generated fault gouge by hyirothermal reaction at high temperature and confirmed that smectites are easily generated in natural.One can evaluate fault activity by ESR dating of fault gouge using an intrinsic ESR signal in smectites。In addition，we found by high energy particles irradiation a new ESR signal in quartz，which is applicable to ESR dating.

First, we inspected the resetting state of ESR signals using the Nojima Fault 500m drilling core samples, and confirmed that ESR signals in the fault gouge had been thermally reduced. This means that fault gouge samples as deep as possible are necessary for complete resetting of ESR signals. As a result of computer simulation on the decay process of ESR signals in the fault gouge, it was found that we should consider as a resetting mechanism not only frictional heat but also vaporization or convection of pore and crystal water in the fault gouge.Next, we carried out chemical analysis of the fault gouge in the 500m core samples to confirm whether or not Pb anomaly actually exists. We analyzed by ICP-MS 8-20 μ m fractions separated from the bulk samples of the fault gouge. As a result we detected extreme ィイD1208ィエD1Pb/ィイD1232ィエD1Th and ィイD1206ィエD1Pb/ィイD1238ィエD1U ratio anomalies from the 0-3mm part just on the fault plane. In the 0-3mm and 3-6mm parts of the fault gouge, the intensity of ィイD1206ィエD1Pb/ィイD1238ィエD1U ratio is larger than that of ィイD1208ィエD1Pb/ィイD1232ィエD1Th ratio, whereas in the parts of more than 6mm away from the fault plane, the intensity of ィイD1206ィエD1Pb/ィイD1238ィエD1U ratio is smaller than that of ィイD1208ィエD1Pb/ィイD1232ィエD1Th ratio. This suggests that the Pb anomaly may not be derived from the migration of the whole Pb isotopes, but from that of apart of ィイD1206ィエD1Pb or ィイD1208ィエD1Pb. The Pb anomaly may be explained by the existence of Rn anomaly.Furthermore we experimentally generated fault gouge by hyirothermal reaction at high temperature and confirmed that smectites are easily generated in natural. One can evaluate fault activity by ESR dating of fault gouge using an intrinsic ESR signal in smectites. In addition, we found by high energy particles irradiation a new ESR signal in quartz, which is applicable to ESR dating.