High-precision multicomponent borehole deformation monitoring

Gladwin, M. T.

doi:10.1063/1.1137704

Cited by 97 publications

(55 citation statements)

References 10 publications

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“…The main sensors in these installations are GTSM strainmeters, each with three horizontal strain gauges placed at 120 • separations along with a fourth redundant gauge offset 30 • from the principal axis (Gladwin, 1984;Gladwin and Hart, 1985). A 3-C Geospace 2 Hz HS-1 seismometer is included as a standard part of these systems.…”

Section: Site Selection Sensors Installation and Well Completionmentioning

confidence: 99%

GONAF – the borehole Geophysical Observatory at the North Anatolian Fault in the eastern Sea of Marmara

Bohnhoff

Dresen

Çeken³

et al. 2017

Sci. Dril.

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Abstract. The Marmara section of the North Anatolian Fault Zone (NAFZ) runs under water and is located less than 20 km from the 15-million-person population center of Istanbul in its eastern portion. Based on historical seismicity data, recurrence times forecast an impending magnitude M>7 earthquake for this region. The permanent GONAF (Geophysical Observatory at the North Anatolian Fault) has been installed around this section to help capture the seismic and strain activity preceding, during, and after such an anticipated event.GONAF (Geophysical Observatory at the North Anatolian Fault) is currently comprised of seven 300 m deep vertical seismic profiling stations and four collocated 100 m deep borehole strainmeters. Five of the stations are located on the land surrounding the Princes Islands segment below the eastern Sea of Marmara and two are on the near-fault Princes Islands south of Istanbul. The 300 m boreholes have 1, 2, and 15 Hz 3-C seismometers near their bottoms. Above this are vertical, 1 Hz, seismometers at ∼ 210, 140, and 70 m depths. The strainmeter boreholes are located within a few meters of the seismometer boreholes and contain horizontal strain tensor sensors and 2 Hz 3-C seismometers at their bottoms. This selection of instruments and depths was made so as to ensure high-precision and broad-frequency earthquake monitoring and vertical profiling, all under low-noise conditions.GONAF is the first ICDP-driven project with a primary focus on long-term monitoring of fault-zone dynamics. It has already contributed to earthquake hazard studies in the Istanbul area in several ways. Combining GONAF recordings with existing regional seismic stations now allows monitoring of the NAFZ offshore of Istanbul down to magnitudes M<0. GONAF also improves the resolution of earthquake hypocenters and source parameters, better defining local fault branches, their seismicity, and earthquake potential. Using its vertical distribution of sensors, it has directly measured depth-dependent seismic side-effects for ground shaking studies. GONAF is starting to address fundamental questions related to earthquake nucleation, rupture dynamics, temporal changes in material properties and strain.

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Section: Site Selection Sensors Installation and Well Completionmentioning

confidence: 99%

GONAF – the borehole Geophysical Observatory at the North Anatolian Fault in the eastern Sea of Marmara

Bohnhoff

Dresen

Çeken³

et al. 2017

Sci. Dril.

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“…Recently GLADWIN (1984) began experimental observation using a borehole measuring unit, where the conventional borehole diameter deformation method is adopted to monitor three components of the horizontal crustal strain. Figure 5 shows the concept of the instrument .…”

Section: Purpose Of Developmentmentioning

confidence: 99%

Borehole-Type Tiltmeter and Three-Component Strainmeter for Earthquake Prediction

Shimada

Sato

1986

J,Phys,Earth

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Borehole-type instruments have many advantages over the conventional instruments usually installed in vaults. The primary merit is that the location is not restricted by geomorphic conditions. This decisively helps us to establish an observation network in a plain field area for earthquake prediction. The borehole-type tiltmeter developed is, as a principle, a pendulum tiltmeter with an electric feedback circuit. Tiltmeters are usually installed in boreholes at depths of about 100 m. Now, we have 23 stations in operation in the Kanto-Tokai area, central Japan. The measuring range is 400 microradian, the resolution is 0.006 microradian, and the long-term stability is better than a few microradian per year. This observation system is expected to be very effective for detecting anomalous tilt changes of the order of 0.05 microradian per day with a time constant of from several hours to tens of days. Recently, an anomalous tilt change of up to 0.4 microradian was detected in the vicinity of the focal area preceding an earthquake of magnitude 6.0. The borehole-type three-component strainmeter invented has a dual cylinder of which the narrow clearance is equally divided into three chambers. Two sets of strainmeters of this type were installed in two boreholes at depths of 160 m at Yasato, Ibaraki-ken.They have often detected strain steps caused by big earthquakes.Detectable strain steps can be as small as 10-10. Strain steps observed by the two instruments agree with each other very well, and are in good harmony with the theoretical strain steps calculated on dislocation models. These facts have proven that instruments of this type have high credibility. Such high performances can be attributed to the fact that the whole system is free from solid friction and less affected by shock and vibration at the time of earthquakes. The future plan is to unify the tiltmeter and the three-component strainmeter to one unit which would be called the Integrated Borehole Observation System (IBOS).

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“…Two-dimensional borehole tensor strainmeters have been well developed since the 1970s both in theory (Pan 1977;Su 1977;Gladwin and Hart 1985;Hart et al 1996;Roeloffs 2010;) and in technique (Ouyang 1977;Gladwin 1984;Ishii 2001;Chi et al 2009). Many such instruments have been deployed in countries such as China, the United States and Japan to monitor tectonic movements related to earthquakes, volcanoes, episodic tremors and slips, and other events (Linde et al 1996;Qiu et al 2007;Wang et al 2008;Hodgkinson et al 2010;Chardot et al 2010;Qiu et al 2011;Hawthorne and Rubin 2013).…”

Section: Introductionmentioning

confidence: 99%

The strain seismograms of P- and S-waves of a local event recorded by four-gauge borehole strainmeter

et al. 2015

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At a sampling rate of 100 samples per second, the YRY-4 four-gauge borehole strainmeters (FGBS) are capable of recording transient strains caused by seismic waves such as P and S waves or strain seismograms. At such a high sampling rate, data from the YRY-4 strainmeters demonstrate fairly satisfactory self-consistency. The strain tensor seismograms demonstrate the senses of motion of P waves, that is, the type of seismic wave travels in the direction of the maximum normal strain change. The observed strain patterns of S waves significantly differ from those of P waves and should contain information about the source mechanism. Spectrum analysis shows that the strain seismograms are consistent with conventional broadband seismograms from the same site.

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High-precision multicomponent borehole deformation monitoring

Cited by 97 publications

References 10 publications

GONAF – the borehole Geophysical Observatory at the North Anatolian Fault in the eastern Sea of Marmara

GONAF – the borehole Geophysical Observatory at the North Anatolian Fault in the eastern Sea of Marmara

Borehole-Type Tiltmeter and Three-Component Strainmeter for Earthquake Prediction

The strain seismograms of P- and S-waves of a local event recorded by four-gauge borehole strainmeter

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