All issues
Volume 53 (2007)
- Issue 4 Pages 335-
- Issue 3 Pages 207-
- Issue 2 Pages 81-
- Issue 1 Pages 1-
Volume 53, Issue 2
Displaying 1-9 of 9 articles from this issue
- |<
- <
- 1
- >
- >|
-
Akito Araya, Wataru Morii, Hideaki Hayakawa, Akiteru Takamori, Takashi ...2007 Volume 53 Issue 2 Pages 81-97
Published: June 25, 2007
Released on J-STAGE: July 05, 2011
JOURNAL FREE ACCESSLaser-interferometric strainmeters have several advantages over conventional quartz-tube and invar-rod strainmeters, such as high sensitivity, low drift, and expandability to long baseline measurements. Of these advantages, low-drift performance is the most significant if a frequency-stabilized laser is used as a light source for the strainmeter . Frequency stabilityreaches values better than 10-1210-13 ; the potential strain accuracy of the laser strainmetercorresponds to these figures. Because strainmeters have a flat response to ground strain change, very broadband observations, such as earth tides, strain steps, and small earthquakes, with a range of 106 -10 Hz, are possible. Strain measurements with reference to a quantum standard that has no drift in principle, such as the wavelength of a frequency-stabilized laser, are essential for the long-term strain measurement of secular and tectonic strain changes. In our observations with the laser strainmeter, however, secular and tectonic changes are unclear, even at a deep undergroundsite. On the other hand, GPS has observed secular and tectonic strain changes; the GPS uses the wavelength of an atomic clock as a reference, which is a quantum standard like a frequency-stabilized laser. After comparing the principle and data of the Kamioka laser strainmeter and other strain meters with those of GPS, we concluded that km-class laser strainmeters can realize long-term strain observations with a higher resolution than GPS. We propose that two-color interfer ometers be constructed in air as a reasonable solution to resolution and cost . With the use of ordinary laser strainmeters (10-100-m baselines), two-color laser strainmeters (1-10-km baselines), and GPS (10-100-km baselines), all of which are based on quantum standards, strain observations can cover a very broad range in both time and space.View full abstractDownload PDF (4288K) -
Hiroshi Ishii, Tsuneo Yamauchi2007 Volume 53 Issue 2 Pages 99-111
Published: June 25, 2007
Released on J-STAGE: July 05, 2011
JOURNAL FREE ACCESSObservation in deep boreholes enables the high S/N ratio observations for detecting very small signals without both artificial noises and meteorological disturbances. Therefore, we have developed multi-component borehole instruments. The instruments are composed of 7 strainmeters (4 horizontal, 2 inclined and one vertical), 2 tiltmeters, 3 seismometers, 4 magnetometers and a quartz thermometer of high resolution. Resolution of A/D conversion of the instruments is 22 bits and sampling rates are 200 Hz for seismometers, 20 Hz for strainmeters, 10 Hz for tiltmeters and 1 Hz for thermometer.
We installed the instruments by cementing at the bottom of the deep boreholes with expansion grout and have constructed borehole array stations. The deepest borehole (JRJ) is 1030m deep and the second (BYB) is 1020 m. Data obtained from the sensors in the instruments are transmitted to the surface by using only one coaxial cable and then sent to our institute(TRIES). We have also constructed data base of collected data from the borehole stations.
We introduce some interesting results obtained from these borehole array stations and how valuable the deep borehole observations are. We also discuss continuous observation forcrustal activity in future.View full abstractDownload PDF (8920K) -
Tadahiro Sato2007 Volume 53 Issue 2 Pages 113-122
Published: June 25, 2007
Released on J-STAGE: March 01, 2011
JOURNAL FREE ACCESSIn relation to the observations that are carried out in horizontal tunnels, several topics are described as applications of the observations to geodynamics studies . The topics discussed are; the free core nutation (FCN), the fluid core resonance (FCR) and the Earth's free oscillations. Long-term observation data obtained from the horizontal tunnels are useful to studya time variation in the FCN and/or the FCR parameters (i.e. its eigen-period, Q-value and strength of the resonance) and to study also the coupling and splitting of the Earth's normal modes. Collaborative observations by strainmeters and gravimeters shall give us useful data to discuss the topics mentioned above.View full abstractDownload PDF (1339K) -
Shuzo Takemoto2007 Volume 53 Issue 2 Pages 123-133
Published: June 25, 2007
Released on J-STAGE: July 05, 2011
JOURNAL FREE ACCESSThis paper is a short historical review of studies for investigating crustal deformations car ried out in Kyoto University during the period from 1909 to 1965. Main topics are (i) Obser vations of Earth tides with tiltmeters and the “Shida number”, (ii) A plan to detect free oscillations of the Earth proposed by Dr. Shida and observations of tidal strains with extensometers, and (iii) Crustal deformations associated with earthquakes. Among others, the Shida's pro posal in 1922 to observe the free oscillations of the Earth should be evaluated more.View full abstractDownload PDF (2113K) -
Development of Equipments Installed in Observation Tunnels and Some Results in Earthquake PredictionTsuneo Yamauchi2007 Volume 53 Issue 2 Pages 135-146
Published: June 25, 2007
Released on J-STAGE: September 07, 2010
JOURNAL FREE ACCESSThis paper reviews of the results of crustal movement observations conducted in Nagoya University. The results are divided into two categories: the first concerns the development of instruments, and the second is related to the research on variations in underground water level. In the first category, we carried out experiments using newly-designed electronic circuits featuring low-cost IC's, and confirmed the long-term stability and reliability of the circuits. We also carried out observation by using silica-tube extensometers equipped with two or three detectors on one component to detect strain steps associated with earthquakes. Our suspension system of silica-tube extensometer is also discussed in this paper, since it is very important in detecting strain step and dynamic strain changes associated with earthquakes. In the second category, we discovered an abnormal increase in groundwater discharge associ ated with earthquake occurrence in a observation tunnel in 1969 using a newly developed equipment. It was found that long-term crustal movements were influenced by changes ingroundwater discharge. We also investigated the strain responses observed after rainfall and succeeded in calculation them using a tank model of precipitations. Abnormal strain re sponses to rainfall are frequently observed before and after earthquake occurrence.View full abstractDownload PDF (1182K) -
Takeyasu Yamamoto2007 Volume 53 Issue 2 Pages 147-156
Published: June 25, 2007
Released on J-STAGE: March 01, 2011
JOURNAL FREE ACCESSThe Japan Meteorological Agency (JMA) has continuously observed crustal movement using primarily volumetric strainmeters and multi-component strainmeters of the borehole type. The main purpose of the observations is to detect any precursory slip of the anticipated Tokai earthquake. Strain observations in the Tokai region are expected to play an important role in providing information about the Tokai earthquake. Tidal strain, atmospheric pressure effects, precipitation effects, and geomagnetic effects are removed from the observed data in real time. The corrected strain is monitored 24 hours a day. Although strain change that had continued over several years due to a long-term slow slip event was not detected, strainchanges continuing for several days to several months due to volcanic activities as well as short-term slow slip events have been detected. The fact that strain changes due to short term slow slip events have been detected suggests that strain observation in the Tokai region has the ability to detect a precursory slip.View full abstractDownload PDF (2019K) -
Duncan Carr Agnew2007 Volume 53 Issue 2 Pages 157-182
Published: June 25, 2007
Released on J-STAGE: September 07, 2010
JOURNAL FREE ACCESSUnlike Japan, the United States has not had a large sustained program to make continuous measurements of crustal deformation-until the Plate Boundary Observatory (PBO) initiative (Section 10) that began in 2003. Most earlier measurements instead were initiatives by individual scientists or particular agencies. In many cases early and promising results have beenfollowed by demonstrations that apparent signals were in fact noise. Partly because of this, few programs have lasted more than a few years, two examples being measurements with shallow strainmeters in the 1960's and shallow tiltmeters in the 1970's. I use some of these his torical examples, and concepts from studies of scientific experimentation, to suggest some general conclusions about this type of measurement.View full abstractDownload PDF (3017K) -
Manabu Hashimoto2007 Volume 53 Issue 2 Pages 183-195
Published: June 25, 2007
Released on J-STAGE: September 07, 2010
JOURNAL FREE ACCESSThe research of crustal deformations based on observations in vaults (hereafter RCDV) for earthquake prediction comes to a deadlock. The one of the most important reasons may be the lack of research plans on the basis of the strategic viewpoints. This program started with out enough knowledge of its targets, precursory deformations to earthquakes in spite of the inflexibility of the system. It is not to be accused considering the state of earthquake science in those days. However it should be criticized that the observation or research system could not follow and digest the development of earthquake science afterward. The enclosure of in formation is also a major problem. In this paper, I review the brief history of the RCDV and point out some intrinsic difficulties. On the basis of this review, I would like to propose that the RCDV should shift their target to crustal dynamics research and borehole type observa tions be given more importance on research of earthquake related strain or tilt changes.View full abstractDownload PDF (6146K) -
Masato Furuya, Keiko Yamamoto2007 Volume 53 Issue 2 Pages 197-202
Published: June 25, 2007
Released on J-STAGE: September 07, 2010
JOURNAL FREE ACCESSDownload PDF (2480K)
- |<
- <
- 1
- >
- >|