Geological structure investigation for 3-dimensional geological structure modeling of a reversed fault belt

Miwa, Atsushi*; Kurosawa, Hideki*

JNC TJ7420 2005-108, 101 Pages, 2004/03

In the 3-dimensional geological structure model, the data of the interpretation of sectional view of the seismic reflecting method, a geologic map, active fault information, and the inversion tectonics of northeast Japan were made reference, and it created on the scale of 1/50,000. As a result of verifying the accuracy of the model as compared with a gravity inquiry result, the error of base rock form is less than 1km. However, base rock form is the accuracy of the synthetic model after the back-arc basin formative period after 15Ma In order for the influence range of an active fault belt to verify from now on, data, such as airborne geophysics and gravity of the accuracy which the modification after the east-and-west strong compression term (2.4Ma or subsequent ones) after inversion tectonics.

Groundwater behavior around of The Western Tottori prefecture Earthquake Source Fault in 2000

Miwa, Atsushi*; Kurosawa, Hideki*

JNC TJ7420 2005-121, 81 Pages, 2003/03

Drastic water level changes in wells near the epicenter were often observed with comparatively large inland earthquakes. Some mechanisms of the co-seismic groundwater level changes were reported. Rojstaczer, (1992) suggested that the earthquake increased rock permeability and temporarily enhanced ground-water flow rates. Sibson (1992) suggested that increase of the crustal strain causes the increase in pore water pressure. In this study, we have investigated the groundwater behaviors in and around the earthquake Source Fault of the Western Tottori prefecture earthquake 2000 by interview and analysis of observed values of the ground water level and of river level.

The Research of chemical composition in the rock near the fault

Miwa, Atsushi*; Kurosawa, Hideki*; Ichikawa, Yasuo*

JNC TJ7420 2005-097, 60 Pages, 2002/03

JNC-TJ7420-2005-097.pdf:18.2MB

Macro- and microscopic structures of the fault rocks included in the core from the 389.52m borehole across the Nojima Fault are described to show the groundwater flow model around the underground fracture zone.

None

Miwa, Atsushi*; Takahashi, Nao*

JNC TJ7420 2005-065, 153 Pages, 2001/03

no abstracts in English

Distribution of active faults

Miwa, Atsushi*; Sasaki, Tatsuya*; Takahashi, Nao*

JNC TJ7420 2005-027, 334 Pages, 2000/03

JNC-TJ7420-2005-027.pdf:53.45MB

It is important study to seize fault activity in order to clarify how effects the active faults influence geo-environment. In this paper, we investigated the distributive character and the activity of active faults with precise aerial photograph interpretation of tectonic landforms. And we prepared fault parameters for this new data by compiling previous results. A number of active faults exist particularly in central Japan. There is a marked regularity in the fault systems between the trend of faults and the sense of the displacement: the reverse fault system distributes in the Northeast Japan with NS-trending, the lateral faults distribute in the Southwest Japan. In particular, NW-trending faults are left-lateral, whereas NE-trending faults are right-lateral. Normal faults are in the central Kyusyu. This implies that the earth's crust of the region is under the same stress system having the maximum principal axis of approximate east-west. Activity of most of the active faults in Japan is class B(10-4 meters per one year). It is limited the distribution of active faults of class A. We presumed when active faults started to move from fault parameters. Active faults in Japan have started at least through a few hundreds thousand years ago.

Investigation of the probability of changing fault activity

Sone, Yoshinori*; Hosoda, Hiroshi*; Miwa, Atsushi*; Shimoyama, Masahiro*

JNC TJ7420 2005-011, 104 Pages, 1999/03

It is important study that to seize development, resumption, pause of fault in the future and probability of changing fault activity. As a result, we will be able to presume the stability of geo-environment. In this paper, we study the inversion tectonics, probability of fault's development, and relationship between distribution of active fault and hypocenter distribution.Regional character of tectonic inversion: in the Northeast Japan, tectonic inversion of normal-reverse fault system (stress of normal-reverse fault type) is mainly developed. In the Southwest Japan, strike-slip inversion (stress of lateral fault type) is mostly developed. Probability of fault's development: With the lapse of time from the period before 2Ma to 2-0.5Ma, the number of fault had increased. With the lapse of time from 2-0.5Ma to 0.5-present time, the number of fault has decreased. This result is opposite from present stress status. It is needful to consider probability of fault's development by investigating the past study.