Piezomagnetic Signals due to Accumulation and Release of Stress on a Plate Boundary Beneath the Tokai Region, Central Japan.
Abstract
This study is a part of an attempt to detect stress changes in Earth's crust by means of geomagnetic observations. Recently developed remote sensing technologies enable us to observe Earth's ground surface deformation. However, the surface deformation is only one aspect of tectonic processes. Therefore, any additional observations are still of considerable importance in understanding the entire processes that occur within Earth's crust. As one of such observations, our group has been conducting geomagnetic observations in the Tokai Region, central Japan, to detect piezomagnetic signals due to stress accumulations. Although we had reported the preliminary results in the 2006 Fall Meeting (Yamazaki et al., 2006), we have conducted a precise data correction, and obtained a reliable result. The mechanism which connects geomagnetic changes and the stress changes is the piezomagnetic effect. In order to clarify the existence of piezomagnetic signals in the observed data, rates of local secular changes in the geomagnetic records are compared with the theoretical ones given by piezomagnetic simulations. In the examination of the observed geomagnetic field changes, the global geomagnetic field variations are excluded from the original records in order to extract only the local signals. In the calculation of the theoretical changes, the piezomagnetic fields generated by back-slips on the plate boundary, the distributions of which have been estimated by Ohta et al. (2004), are estimated. Observed and calculated values exhibit a good correlation, which implies that the observed local geomagnetic field changes are piezomagnetic signals. It is widely recognized that geomagnetic field changes due to piezomagnetic effects are generally too small to be detected. However, many studies have also pointed out that stress sensitivities of the piezomagnetic effect can be amplified in the actual crust. The result of our present study indicates that the intensity of the piezomagnetic field in the Tokai region is sufficiently large to be observed. This means that observations of the geomagnetic field can be one of probes to monitor stress changes in the region.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFM.S53B1827Y
- Keywords:
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- 1532 Reference fields: regional;
- global;
- 1540 Rock and mineral magnetism;
- 1555 Time variations: diurnal to decadal;
- 8150 Plate boundary: general (3040);
- 8164 Stresses: crust and lithosphere