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Volume 53 (2007)
- Issue 4 Pages 335-
- Issue 3 Pages 207-
- Issue 2 Pages 81-
- Issue 1 Pages 1-
Volume 53, Issue 4
Displaying 1-5 of 5 articles from this issue
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Osam Sano, Atsuo Hirata2007 Volume 53 Issue 4 Pages 335-348
Published: December 25, 2007
Released on J-STAGE: September 07, 2010
JOURNAL FREE ACCESSMethods of measuring contemporary stress are briefly reviewed with particular interest in precise measurements at depth. Stress-relief methods are widely used techniques in the engineering field. Wireless strain-cells indicate the high possibility of stress-relief methods for deep wells. Numerical calculation on the stress field within the elastically coupled materials, [rock + mortar + strain-meter], shows that the stress inside the over-cored rock is not completely relieved. More reliable results can be given by such analysis than that without considering residual stress effects. The hydraulic fracturing method has been widely used in the geophysical field. However, serious suspicions about the interpretation of reopening pressure have also been raised in the past 20 years. As possible answers to these suspicions have been proposed recently, it is necessary to check the past results again and cross-check the results of different methods. Non-hydrofracturing methods are free from problems associated with the permeation of pressure fluid into artificial fracture and borehole wall. Furthermore, some non-hydrofracturing methods do not need the assumption of principal stresses having a constant direction, which can be an advantage over hydrofracturing methods for long-term observations of stress variations. Core-based and boreholewall-fracture-based methods, unfortunately, cannot now be considered to be precise measurement methods. However, these methods have the potential to estimate stress, particularly at great depths.View full abstractDownload PDF (4408K) -
Minoru Kasahara, Muneo Okayama, Masayosi Ichiyanagi, Masamitsu Takada, ...2007 Volume 53 Issue 4 Pages 349-357
Published: December 25, 2007
Released on J-STAGE: September 07, 2010
JOURNAL FREE ACCESSA brief review of continuous crustal movement observation conducted by Hokkaido University since 1971 is presented. The first observatory was established near Erimo Cape at the southern tip of Hokkaido island in 1971. Data from 13 vault type and 6 borehole type stations, which consist of three components of strain-meter and two components of tilt-meter, are transfered by a telemeter system with 24-bits ADC and 1 Hz sampling rate in 2006. In 1973 clear pre-, co-, and post-, seismic crustal deformations were recorded at Erimo station related to the 1973 Nemuro-hanto-oki (MW7.7) earthquake which occurred at 250 km north-east of the station. However, no clear pre-seismic crustal deformation was observed related to the 2003 Tokachi-oki (MW8.0) that occurred at 100km east of the station. Clear co-and post-seismic deformations related to this event were recorded at several stations. Especially, it should be noted that complete strain seismograms of Mw -8 event were recorded by the new recording system at MYR station nearest the source of the event.View full abstractDownload PDF (4099K) -
Masaaki Mishina2007 Volume 53 Issue 4 Pages 359-368
Published: December 25, 2007
Released on J-STAGE: July 05, 2011
JOURNAL FREE ACCESSContinuous observation of crustal deformation in Tohoku University was begun in the late 1960's. At present, more than 20 observation stations are operated. At older stations extensometers and watertube tiltmeters were installed in a tunnel. At newly established stations, borehole strainmeter (volumetric strainmeter or 3-component strainmeter)and borehole tiltmeters were installed at a depth of from 100 to 500m. Many researches based on the continuous observation were performed up to 2000. Development of instruments and investigation on strain migration were performed in the 1970's. In the 1980's and the 1990's strain changes related to big earthquake (e. g. 1983 Nihonkai-Chubu Earthquake, 1994 Sanriku Haruka Oki Earthquake, etc.) were analyzed, and pre-seismic and post-seismic slip of earthquakes were detected on the strain records. Although experimental method to correct annual change and short term noise caused by precipitation are not yet developed well, we can recognize the accordance of change in strain trend with seismicity off Sanriku area. Characteristics of secular change, annual change and short term noise are not understood well for borehole sites.View full abstractDownload PDF (3041K) -
Ichiro Kawasaki2007 Volume 53 Issue 4 Pages 369-377
Published: December 25, 2007
Released on J-STAGE: September 07, 2010
JOURNAL FREE ACCESSWe discuss significance in continuous observation of crustal movement in Japan. One is an earthquake prediction, while the other should be a basic study of solid Earth dynamics. In the first part, we compare merits and demerits of the continuous recording of crustal movement with those of SG and GPS in terms of monitoring of interseismic/preseismic crustal deformation in Japan. In the remaining part, we compare running spectra of the continuous recording of crustal movement at four stations in Japan after the 2004 Sumatra-Andaman earthquake, showing that they record signals of free oscillations of an order of 10-10 strains at periods from thousand second to hours. We conclude that the continuous recording of crustal movement should be a powerful tool for studies both in earthquake prediction and solid Earth dynamics.View full abstractDownload PDF (4085K) -
Kachishige Sato2007 Volume 53 Issue 4 Pages 379-385
Published: December 25, 2007
Released on J-STAGE: September 07, 2010
JOURNAL FREE ACCESSDownload PDF (2597K)
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