Age dating fault gouge how accurate are dating scans
The fracture zone confines to the crystalline basement, and is spatially coincident with the elongation of the isoseismals of the 1994 mainshock and a 10-km-long WNW-ESE trending topographic lineament.
The preliminary results from the electron spin resonance (ESR) dating on the quartz grains from the fault gouge indicate that the last major faulting in this site occurred 430 ± 43 ka ago.
On the other hand, the ESR age obtained from the MTL is younger than the KAr age (about 11 Ma), which is presumably overestimated due to the existence of the source minerals in the KAr dating sample.
Since it is geologically known that the MTL at the outcrop had moved until the Late Pleistocene-Holocene, the fault movement of the MTL at this outcrop probably began at 6.76–9.28 Ma B. after the intrusion of the felsitic dyke (12–16 Ma) which is the source rock of the fault gouge into the fault boundary.
The ESR dating method has been applied to the fault gouge of the Nojima Fault, the outcrop of which arose due to the southern Hyogo Prefecture Earthquake on January 17th, 1995, and to the fault gouge of the Median Tectonic Line (MTL) which is a major active fault in Japan, without considering the resetting of ESR signals.
The ESR ages obtained for clay minerals in the fault gouges are considered to indicate the age of the beginning of the fault movements at the outcrop.
The basic assumption of zeroing of geological thermoluminescence during faulting was examined using techniques such as mechanoluminescence and clay mineralogy.In conjunction with other evidences from the lacustrine records in the region, phases of regionally extended tectonic activities at about 40 ka and 60 ka are inferred.