Publication Date:
2020-02-24
Description:
We used a field analysis of rock deformation microstructures and mesostructures to reconstruct
the long-term orientation of stresses around two major active fault systems in Japan, the Median Tectonic
Line and the Rokko-Awaji Segment. Our study reveals that the dextral slip of the two fault systems, active
since the Plio-Quaternary, was preceded by fault normal extension in the Miocene and sinistral wrenching in
the Paleogene. The two fault systems deviated the regional stress field at the kilometer scale in their vicinity
during each of the three tectonic regimes. The largest deviation, found in the Plio-Quaternary, is a more fault
normal rotation of the maximum horizontal stress to an angle of 79° with the fault strands, suggesting an
extremely low shear stress on the Median Tectonic Line and the Rokko-Awaji Segment. Possible causes of this
long-term stress perturbation include a nearly total release of shear stress during earthquakes, a low static
friction coefficient, or lowelastic properties of the fault zones compared with the country rock. Independently of
the preferred interpretation, the nearly fault normal orientation of the direction of maximum compression
suggests that the mechanical properties of the fault zones are inadequate for the buildup of a pore fluid
pressure sufficiently elevated to activate slip. The long-term weakness of the Median Tectonic Line and the
Rokko-Awaji Segment may reside in low-friction/low-elasticity materials or dynamic weakening rather than in
preearthquake fluid overpressures.
Description:
Published
Description:
1900–1919
Description:
2T. Tettonica attiva
Description:
JCR Journal
Description:
reserved
Keywords:
Kilometer-scale deviation of the regional stress fields around the two faults
;
Rotations of the direction of maximum compression reveal fault weakness
;
Fault weakness does not reside in static, preearthquake fluid overpressure
;
04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
Permalink
