Crack density, saturation rate and porosity at the 2001 Bhuj, India, earthquake hypocenter: a fluid-driven earthquake?

Mishra, O. P.; Zhao, Dapeng

doi:10.1016/s0012-821x(03)00285-1

Cited by 195 publications

(95 citation statements)

References 35 publications

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“…The processes inducing microcracking such as thermal cooling are beyond the scope of this paper. This approach is consistent with previous studies (Zhao and Mizuno, 1999;Mishra and Zhao, 2003;Adelinet et al, 2011). The next step consists in identifying the mechanisms that can explain our results keeping in mind that crack density is constant.…”

Section: Discussionsupporting

confidence: 93%

“…This can be achieved by integrating the forward effective model into an optimization process. Such idea was developed in active geological areas by Zhao and Mizuno (1999) and Mishra and Zhao (2003) who characterized the hypocenter locations of the Kobe (1995) and Buhj (2001) earthquakes in terms of crack density and saturation rate. On the other hand, Adelinet et al (2011) focused on passive microseismicity data: they estimated the spatial distributions of the crack density and the fluid bulk modulus beneath the Reykjanes Peninsula thanks to accurate tomography data.…”

Section: Introductionmentioning

confidence: 99%

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Crack Features and Shear-Wave Splitting Associated with Fracture Extension during Hydraulic Stimulation of the Geothermal Reservoir in Soultz-sous-Forêts

Adelinet

Dorbath

Calò

et al. 2015

Oil Gas Sci. Technol. – Rev. IFP Energies nouvelles

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-The recent tomography results obtained within the scope of the Enhanced Geothermal System (EGS) European Soultz project led us to revisit the meso-fracturing properties of Soultz test site. In this paper, we develop a novel approach coupling effective medium modeling and shear-wave splitting to characterize the evolution of crack properties throughout the hydraulic stimulation process. The stimulation experiment performed in 2000 consisted of 3 successive injection steps spanning over 6 days. An accurate 4-D tomographic image was first carried out based upon the travel-times measured for the induced seismicity [Calò M., Dorbath C., Cornet F.H., Cuenot N. (2011) Large-scale aseismic motion identified through 4-D P-wave tomography, Geophys. J. Int. 186, 1295Int. 186, -1314. The current study shows how to take advantage of the resulting compressional wave (Calò et al., 2011) and shear-wave velocity models. These are given as input data to an anisotropic effective medium model and converted into crack properties. In short, the effective medium model aims to estimate the impact of cracks on velocities. It refers to a crack-free matrix and 2 families of penny-shaped cracks with orientations in agreement with the main observed geological features: North-South strike and dip of 65°East and 65°West [Genter A., Traineau H. (1996) Analysis of macroscopic fractures in granite in the HDR geothermal well EPS-1, Soultz-sousForêts, France, J. Vol. Geoth. Res. 72, 121-141], respectively. The resulting output data are the spatial distributions of crack features (lengths and apertures) within the 3-D geological formation. We point out that a flow rate increase results in a crack shortening in the area imaged by both compressional and shear waves, especially in the upper part of the reservoir. Conversely, the crack length, estimated during continuous injection rate phases, is higher than during the increasing injection rate phases. A possible explanation for this is that cracks remain large because the system has time to relax. We also calculate the extension and opening rates during all hydraulic stimulation sets. While the opening rate is unchanged, the extension rate varies depending on the stimulation phase. It is also shown to be higher around and above the open-hole section than below. This can indicate a potential upward path that makes fluid percolation easier within the granite formation, this path being induced by the temperature gradient. We also compare the evolution of crack extension during injection with shear-wave splitting. Split shear waves were recorded at 2 stations during hydraulic stimulation and processed in terms of splitting parameters. The fast shear-wave polarization remains constant and parallel to the maximum horizontal stress orientation while the amplitude of splitting varies with time. We observe a good agreement between travel-time differences and crack extension rates during the first 4 days of the stimulation experiment. Afterwards, these two parameters depart from each other. This stud...

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Section: Discussionsupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Crack Features and Shear-Wave Splitting Associated with Fracture Extension during Hydraulic Stimulation of the Geothermal Reservoir in Soultz-sous-Forêts

Adelinet

Dorbath

Calò

et al. 2015

Oil Gas Sci. Technol. – Rev. IFP Energies nouvelles

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“…The higher b-values beneath the mainshock could be due to high crack density, high saturation rate, high porosity and strong heterogeneities (Mishra and Zhao 2003;Singh et al 2011). In case of low ambient stress, the accumulated stress varies from very low to the breaking strength levels in contrast to high ambient stress where amplitude of this variation ranges from moderate values to the same maximum breaking strength.…”

Section: Resultsmentioning

confidence: 99%

“…We relocated the large set of aftershocks of the 2001 Bhuj earthquake in this study using HypoDD in a similar way as used by Mishra et al (2008) in relocating their old dataset (Mishra and Zhao 2003). The double-difference (HypoDD) algorithm incorporates ordinary absolute travel-time measurements and/or cross-correlation of P and S-wave differential travel-time measurements to determine high-resolution hypocentre locations (Waldhauser and Ellsworth 2000).…”

Section: Relocation Of Aftershock Sequences By Hypoddmentioning

confidence: 99%

“…Such changes are due to increase in crustal heterogeneities (Aki 1965;Wiemer and Wyss 1997;Wyss et al 2004), fluid-filled fractured rock mass. The strong heterogeneities within a mafic pluton are responsible for the accumulation of large crustal shear stress that results a lower crustal intraplate earthquake in this region (Kayal et al 2002;Mishra and Zhao 2003;Mandal et al 2004;Mandal and Pujol 2006;Mandal and Chadha 2008).…”

Section: Estimates Of 3d B-values Mapping In the 2001mentioning

confidence: 99%

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Spatial variation of the aftershock activity across the Kachchh Rift Basin and its seismotectonic implications

Singh

Mishra²,

Kumar

et al. 2012

J Earth Syst Sci

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We analyzed 3365 relocated aftershocks with magnitude of completeness (Mc) ≥1.7 that occurred in the Kachchh Rift Basin (KRB) between August 2006 and December 2010. The analysis of the new aftershock catalogue has led to improved understanding of the subsurface structure and of the aftershock behaviour. We characterized aftershock behaviour in terms of a-value, b-value, spatial fractal dimension (D s ), and slip ratio (ratio of the slip that occurred on the primary fault and that of the total slip). The estimated b-value is 1.05, which indicates that the earthquake occurred due to active tectonics in the region. The three dimensional b-value mapping shows that a high b-value region is sandwiched around the 2001 Bhuj mainshock hypocenter at depths of 20-25 km between two low b-value zones above and below this depth range. The D s -value was estimated from the double-logarithmic plot of the correlation integral and distance between hypocenters, and is found to be 2.64 ± 0.01, which indicates random spatial distribution beneath the source zone in a two-dimensional plane associated with fluid-filled fractures. A slip ratio of about 0.23 reveals that more slip occurred on secondary fault systems in and around the 2001 Bhuj earhquake (Mw 7.6) source zone in KRB.

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Seismicity, faulting, and structure of the Koyna‐Warna seismic region, Western India from local earthquake tomography and hypocenter locations

et al. 2014

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Although seismicity near Koyna Reservoir (India) has persisted for~50 years and includes the largest induced earthquake (M 6.3) reported worldwide, the seismotectonic framework of the area is not well understood. We recorded~1800 earthquakes from 6 January 2010 to 28 May 2010 and located a subset of 343 of the highest-quality earthquakes using the tomoDD code of Zhang and Thurber (2003) to better understand the framework. We also inverted first arrivals for 3-D Vp, Vs, and Vp/Vs and Poisson's ratio tomography models of the upper 12 km of the crust. Epicenters for the recorded earthquakes are located south of the Koyna River, including a high-density cluster that coincides with a shallow depth (<1.5 km) zone of relatively high Vp and low Vs (also high Vp/Vs and Poisson's ratios) near Warna Reservoir. This anomalous zone, which extends near vertically to at least 8 km depth and laterally northward at least 15 km, is likely a water-saturated zone of faults under high pore pressures. Because many of the earthquakes occur on the periphery of the fault zone, rather than near its center, the observed seismicity-velocity correlations are consistent with the concept that many of the earthquakes nucleate in fractures adjacent to the main fault zone due to high pore pressure. We interpret our velocity images as showing a series of northwest trending faults locally near the central part of Warna Reservoir and a major northward trending fault zone north of Warna Reservoir.

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Crack density, saturation rate and porosity at the 2001 Bhuj, India, earthquake hypocenter: a fluid-driven earthquake?

Cited by 195 publications

References 35 publications

Crack Features and Shear-Wave Splitting Associated with Fracture Extension during Hydraulic Stimulation of the Geothermal Reservoir in Soultz-sous-Forêts

Crack Features and Shear-Wave Splitting Associated with Fracture Extension during Hydraulic Stimulation of the Geothermal Reservoir in Soultz-sous-Forêts

Spatial variation of the aftershock activity across the Kachchh Rift Basin and its seismotectonic implications

Seismicity, faulting, and structure of the Koyna‐Warna seismic region, Western India from local earthquake tomography and hypocenter locations

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