Fault Zone Resistivity Structure and Monitoring at the Taiwan Chelungpu Drilling Project (TCDP)

Chiang, Cheng-Yen; Unsworth, Martyn; Chen, Chow Son; Chen, Chien Chih; Lin, A. T.; Hsu, Han

doi:10.3319/tao.2008.19.5.473(t)

Cited by 8 publications

(6 citation statements)

References 30 publications

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“…In a broad view, three are significant low resistivity zones surveyed by the magnetotelluric method (see Chiang et al 2008). Two shallow zones are associated with subsurface aquifers (see Yeh et al 2007).…”

Section: Subsurface Structure Physical Properties and Log Unitsmentioning

confidence: 99%

Core-log integration studies in hole-A of Taiwan Chelungpu-fault Drilling Project

Yeh

Dong

et al. 2008

Geophysical Journal International

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S U M M A R YTaiwan Chelungpu-fault Drilling Project (TCDP) was initiated to understand the physical mechanisms involved in the large displacements of the 1999 Taiwan Chi-Chi earthquake. Continuous measurements of cores (including laboratory work) and a suite of geophysical downhole logs, including P-and S-wave sonic velocity, gamma ray, electrical resistivity, density, temperature, electrical borehole images and dipole-shear sonic imager, were acquired in Hole-A over the depth of 500-2003 m. Integrated studies of cores and logs facilitate qualitative and quantitative comparison of subsurface structures and physical properties of rocks. A total of 10 subunits were divided on the basis of geophysical characteristics. Generally, formation velocity and temperature increase with depth as a result of the overburden and thermal gradient, respectively. Gamma ray, resistivity, formation density, shear velocity anisotropy and density-derived porosity are primarily dependent on the lithology. Zones with changes of percentage of shear wave anisotropy and the fast shear polarization azimuth deduced from Dipole Shear-Imager (DSI) are associated with the appearance of fractures, steep bedding and shear zones. The fast shear wave azimuth is in good agreement with overall dip of the bedding (approximately 30 • towards SE) and maximum horizontal compressional direction, particularly in the Kueichulin Formation showing strong shear wave velocity anisotropy. Bedding-parallel fractures are prevalent within cores, whereas minor sets of high-angle, NNW-SSE trending with N-and S-dipping fractures are sporadically distributed. The fault zone at depth 1111 m (FZA1111) is the Chi-Chi earthquake slip zone and could be a fluid conduit after the earthquake. The drastic change in fast shear wave polarization direction across the underlying, non-active Sanyi thrust at depth 1710 m reflects changes in stratigraphy, physical properties and structural geometry.

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Section: Subsurface Structure Physical Properties and Log Unitsmentioning

confidence: 99%

Core-log integration studies in hole-A of Taiwan Chelungpu-fault Drilling Project

Yeh

Dong

et al. 2008

Geophysical Journal International

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“…The result indicates that Archie's equation is dominated primarily by R w and "m" values. Thus, we define m = 1.5 in agreement with previous MT research (Chiang et al 2008) as suitable to assess the fluid content in the fault zone. The pore fluid resistivity is affected only by temperature, with the interconnected fluid estimation in 1.8 -4.6% range (blue dashed line shown in Fig.…”

Section: Discussionmentioning

confidence: 62%

“…Additionally, the average shear and twist value histograms (Figs. 3a, b) seem higher than those for the Western Foothills in Central Taiwan (Chiang et al 2008). The shear values were primarily within the ±40° range and the twist values within the ±30° range over whole periods.…”

Section: Mcneice-jones Schemementioning

confidence: 92%

“…The effective porosity typically decreases exponentially with depth (Rubey and Hubbert 1959) without a damage zone associated with a fault zone. Brines are widely distributed within sediment in depth based on the Taiwan tectonic setting (Chiang et al 2008(Chiang et al , 2010Bertrand et al 2009). Saline aqueous fluids are good electrical conductors and laboratory studies have shown that brine electrical resistivity depends on the salinity, pressure and temperature (Sourirajan and Kennedy 1962).…”

Section: Discussionmentioning

confidence: 99%

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An Investigation of the 3D Electrical Resistivity Structure in the Chingshui Geothermal Area, NE Taiwan

Chiang¹,

Hsu²,

Chen³

2015

Terr. Atmos. Ocean. Sci.

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The Chingshui geothermal area southwest of the Ilan plain is identified as a western extension of the Okinawa Trough in the northern Taiwan subduction system. Numerous geophysical, geological and geochemical investigations have been conducted since the 1970s by the Industrial Technology Research Institute, the Chinese Petroleum Corporation of Taiwan and the National Science Council of Taiwan. These studies indicated that the Chingshui stream is one of the largest geothermal areas for electricity generation in Taiwan. However, the power generation efficiency has not met initial expectations. Magnetotelluric (MT) data analyses show that the Chingshui geothermal region is a geologically complex area. A full three-dimensional (3D) inversion was therefore applied to reprocess the MT data and provide the detailed electrical structure beneath the Chingshui geothermal region. The 3D geoelectrical model displays an improved image that clearly delineates the Chingshui geothermal system geometry. Two conductive anomalies are imaged that possibly indicate high potential areas for geothermal energy in the Chingshui geothermal system. One of the potential areas is located in the eastern part of the Chingshui Fault at shallow depths. A significant conductive anomaly is associated with high heat flow and fluid content situations southwest of the geothermal manifest area at depth. A higher interconnected fluid indicates that this area contains the highest potential for geothermal energy in the Chingshui geothermal system.

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“…Even though many magnetotelluric explorations have investigated deep electrical structures on Taiwan (Bertrand et al, 2009;Bertrand et al, 2012;Chiang et al, 2011a;Chiang et al, 2015;Chiang et al, 2008), there were no marine electromagnetic experiments around Taiwan until 2010. The first MCSEM survey was carried out for gas hydrate investigations offshore SW Taiwan (Hsu et al, 2014).…”

Section: Marine Electromagnetic Exploration Is a Geophysical Prospectmentioning

confidence: 99%

Evaluations of an ocean bottom electro-magnetometer and preliminary results offshore NE Taiwan

Lin¹,

Chiang²,

Huang³

et al. 2019

Preprint

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Abstract. The first stage of field experiments involving the design and construction of a low-power consumption ocean bottom electro-magnetometer (OBEM) has been completed. To improve the performance of the OBEM, we rigorously evaluated each of its units, e.g., the data loggers, acoustic parts, internal wirings, and magnetic and electric sensors, to eliminate unwanted events such as unrecovered or incomplete data. The evaluations of the procedure included the following. Data logger: digitizer sensitivity, linearity, and errors Acoustic transceiver: “ENABLE,” “DISABLE,” “RANGE,” “RELEASE1,” “RELEASE2,” and “OPTION1” functions Magnetic sensor: sensitivity of the fluxgate and orthogonality Electrical receiver: potential voltage, impedance, and frequency responses Power consumption: the maximum operating current of two sets of batteries Deployment and recovery procedures on deck We confirmed the optimal performance of the OBEM after repeatedly testing the procedures. The first offshore deployment of the OBEM together with ocean bottom seismographs (OBSs) was performed in NE Taiwan, where the water depth is approximately 1,400 m. The total intensity of the magnetic field (TMF) measured by the OBEM varied in the range of 44,100–44,150 nT, which corresponded to the proton magnetometer measurements. The daily variations of the magnetic field were recorded using the two horizontal components of the OBEM magnetic sensor. We found that the inclinations and magnetic data of the OBEM varied with two observed earthquakes when compared to the OBS data. The potential fields of the OBEM were slightly, but not obviously, affected by the earthquakes.

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Fault Zone Resistivity Structure and Monitoring at the Taiwan Chelungpu Drilling Project (TCDP)

Cited by 8 publications

References 30 publications

Core-log integration studies in hole-A of Taiwan Chelungpu-fault Drilling Project

Core-log integration studies in hole-A of Taiwan Chelungpu-fault Drilling Project

An Investigation of the 3D Electrical Resistivity Structure in the Chingshui Geothermal Area, NE Taiwan

Evaluations of an ocean bottom electro-magnetometer and preliminary results offshore NE Taiwan

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