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Professor Wong's research interest is in rock mechanics, with focus on earthquake mechanics, energy resources and environmental applications. He investigates both the phenomenological and micromechanical aspects of rock deformation and fluid flow, using an approach integrating high-pressure deformation experiment, quantitative characterization of microstructure and theoretical analysis.

Brittle-Ductile Transition and Permeability Evolution in Porous Rock 

A broad spectrum of failure modes are observed in sedimentary formations. It is important to understand the mechanics of failure, development of strain localization and evolution of permeability, in relation to various seismotectonic and geotechnical problems, including the characterization and prediction of reservoir compaction, borehole instability, fluid flow and induced seismicity. We have been investigating these phenomena in both clastic and carbonate rocks with a wide range of porosities. Our mechanical data for a broad range of pressure conditions have established the dynamic links among stress-induced porosity change, damage evolution, failure and yield envelopes, and the development of localized versus delocalized failure. 

In such rock mechanics investigations, it is essential to integrate detailed microstructural and acoustic emission measurements which can elucidate the microscale deformation mechanisms and provide the link to field observations of damage. We have utilized a broad range of imaging techniques, including 3-dimensional visualization by laser scanning confocal microscope and synchrotron microCT. Analytic modeling and numerical simulation (using finite element and discrete element methods) are used to gain insights into the micromechanics of dilatant and compactant failure. 

Fluid exerts significant mechanical and chemical effects on virtually all crustal processes. Since permeability change is coupled to tectonic deformation, the realistic modeling of fluid percolation process requires knowledge of the magnitude and stress dependence of permeability in crustal rocks. A wide-range permeameter is used for hydraulic transport measurements under triaxial compression. The evolution of permeability and its anisotropy are being investigated as functions of stress and damage development, in relation to various failure modes.

Strength and Permeability of Core Samples from SAFOD and TCDP  

The San Andreas Fault Observatory at Depth (SAFOD) has been designed to directly monitor an active fault zone at seismogenic depth, to sample fault rocks and fluids, and to measure a broad spectrum of geophysical and geochemical properties. As part of EarthScope, the overall objective of SAFOD is to provide new insights that can answer the many fundamental questions on the physical and chemical processes operative within the San Andreas and other major plate-bounding faults that have remained unresolved. One important component of SAFOD is the characterization of the composition, origin, deformation mechanisms, frictional behavior and physical properties (permeability, seismic properties, etc.) of core samples. In collaboration with the USGS Menlo Park rock physics laboratory, we have acquired a comprehensive data set on the hydromechanical properties of core and cuttings from SAFOD phases 1 and 2, which provide important constraints on the strength, poromechanical behavior and potential weakening mechanisms in the San Andreas fault system. The SAFOD drilling strategy intentionally limited the amount of core retrieved during the initial phases to <1% , but continuous coring is planned for Phase 3 drilling in 2007. The availability of significantly more cores from multilateral drilling will then provide an unique opportunity to explore these issues in a more comprehensive and thorough manner. 

The Taiwan Chelungpu-fault Drilling Project (TCDP) was initiated to drill two vertical holes into the northern portion of the Chelungpu fault that ruptured during the Chi-Chi earthquake in 1999. We are systematically characterizing the hydromechanical properties of core samples from hole A which was drilled to a depth of 2 km, penetrating the Chelungpu thrust. While the overall objectives of TCDP and SAFOD are very similar, the Chelungpu and San Andreas fault systems are associated with very different tectonic settings, styles of faulting and earthquake cycles. Seismological and geodetic measurements indicate that the Chi-Chi earthquake may involve dynamic weakening mechanisms which are sensitively dependent on the strength, permeability and poromechanical properties. In parallel with our current efforts to study the SAFOD samples, the study of TCDP samples can potentially lead to synergistic understanding of some important questions on earthquake mechanics that remain unresolved. 

Other questions on earthquake mechanics are also of interest. The investigation of frictional sliding is important for understanding earthquake mechanics issues, such as how the friction constitutive relation may influence the stress drop and recurrence time of earthquake cycles. It has been recognized from field and laboratory observations that deformation and metamorphism are closely interlinked. The decomposition of hydrous phases during prograde metamorphism may lead to embrittlement and weakening, with important implications on the mechanics of overthrusting. We have been studying the development of embrittlement and weakening induced by dehydration, and their complex interplay with fluid drainage and reaction kinetics.

Submarine Groundwater Discharge, Saltwater Intrusion and Tidal Influence  

Groundwater can flow directly into the sea by seeping from unconfined aquifers into the near shore or from confined aquifers found underneath continental shelves further from shore. Previous worldwide estimates of this submarine groundwater discharge (SGD) range from 0.01% to 10% of surface-water runoff. Since SGD has significant impact on near-shore transport mechanisms and therefore a major influence on the flux of chemicals into the ocean, it is imperative to quantify the spatio-temporal complexity of the discharge and its interplay with saltwater intrusion and tidal influence. An ultrasonic seepage meter was developed for the continuous measurement of SGD at rates as low as 0.1 µm/s. The ultrasonic seepage meter has been deployed in numerous sites on Long Island, as well as other localities in this country and overseas. Current efforts focus on the integration of SGD measurement with geophysical logging (including electrical conductivity and streaming potential) to map out the spatial extend of SGD

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Patents, Books and Selected Publications  

Smith, C., R. Paulsen, and T.-f. Wong, Ultrasonic Seepage Meter, U.S. Patents 6,874,371 (4/5/2005); 7,107,859 (9/19/2006).

 (Chen, Y., and T.-f. Wong, "Rock Physics" ), Peking University Press, Beijing, China, 231 pp, 2001.

Paterson, M.S. and Wong, T.-f., Experimental Rock Deformation - The Brittle Field, 2nd Edition. Springer-Verlag, New York, 348 pp., 2005.

Wang, B. S., Y. Chen, and T.-f. Wong, A discrete element model for the development of compaction localization in granular rock, in press, J. Geophys. Res., 2008.

Louis, L., T.-M. N. Chen, C. David, P. Robion, T.-f. Wong, and S.-R. Song, Anisotropy of magnetic susceptibility and P-wave velocity in core samples from the Taiwan Chelungpu-fault Drilling Project (TCDP), submitted, J. Struct. Geol., 2007.

Tembe, S., D. A. Lockner, and T.-f. Wong, Effect of clay content and mineralogy on frictional sliding behavior of simulated gouges: Binary and ternary mixtures of quartz, illite and montmorillonite, submitted, J. Geophys. Res., 2007.

Tembe, S., P. Baud, and T.-f. Wong, Stress conditions for the propagation of discrete compaction bands in porous sandstone, submitted, J. Geophys. Res., 2007.

Tembe, S., V. Vajdoda, P. Baud, W. Zhu, and T.-f. Wong, A new methodology to delineate the compactive yield cap of two porous sandstones under undrained condition, Mech. Mat., 39, 513-523, 2007.

Louis, L., T.-f. Wong, and P. Baud, Imaging strain localization by X-ray radiography and digital image correlation: deformation bands in Rothbach sandstone, J. Struct. Geol., 29, 129-140, 2007.

Morrow, C.A, J. G. Solum, S. Tembe, D.A. Lockner, and T.-f. Wong, Using drill cutting separates to estimate the strength of narrow shear zones at SAFOD, Geophys. Res. Lett., 34, L11301, doi:101029/2007GL029665, 2007.

Wong, T.-f. and W. Zhu, Weak elastic anisotropy in a cracked rock, in Rock Physics and Geomechanics in the Study of Reservoirs and Repositories, ed. C. David and M. le Ravalec-Dupin, Geological Society of London Special Publication 284, 207-220,, 2007.

Louis, L., P. Baud, and T.-f. Wong, Effect of image resolution on the spatial distribution of X-ray attenuation in sandstone, in Rock Physics and Geomechanics in the Study of Reservoirs and Repositories, ed. C. David and M. Le Ravalec-Dupin, Geological Society of London Special Publication 284, 127-146, 2007.

Zhu, W., L. G. J. Montesi, and T.-f. Wong, A probabilistic damage model of stress-induced permeability anisotropy during cataclastic flow, J. Geophys. Res., 112, B10207, doi:10.1029/2006JB004456, 2007.

Baud, P., V. Vajdova, and T.-f. Wong, Shear-enhanced compaction and strain localization: Inelastic deformation and constitutive modeling of four porous sandstones, J. Geophys. Res., 111, B12401, doi: 10.1029/2005JB004101.2006.

Tembe, S., V. Vajdova, T.-f. Wong, and W. Zhu, Initiation and propagation of strain localization in circumferentially notched samples of two porous sandstones, J. Geophys. Res., 111, B02409, doi:10.1029/2005JB003611, 2006.

Wong, T.-f., R.H.C. Wong, K.T. Chau, and C. A. Tang, Microcrack statistics, Weibull distribution and micromechanical modeling of compressive failure in rock, Mech. Mat., 38, 664-681, 2006.

Louis, L., T.-f. Wong, P. Baud, and S. Tembe, Imaging strain localization by X-ray computed tomography: discrete compaction bands in Diemelstadt sandstone, J. Struct. Geol., 28, 762-775, 2006.

Tembe, S., D.A. Lockner, J. Solum, C. Morrow, T.-f. Wong, and D.E. Moore, Frictional Strength of Cuttings and Core from SAFOD Drillhole Phases 1 and 2, Geophys. Res. Lett., 33, L23307, doi: 10.1029/2006GL0276262006, 2006.

Wong, T.-f., C. David, and B. Menéndez, Mechanical compaction, in Mechanics of Fluid Saturated Rocks, ed. Y. Guéguen and M. Boutéca, Academic Press, p55-114, 2004.

Baud, P., E. Klein, and T.-f. Wong, Compaction localization in porous sandstones: Spatial evolution of damage and acoustic emission activity, J. Struct. Geol., 26, 603-624, 2004.

Vajdova, V., P. Baud, and T.-f. Wong, Compaction, dilatancy and failure in porous carbonate rocks J. Geophys. Res., 109, B05204, doi:10.1029/2003JB002508, 2004.

Vajdova, V., P. Baud, and T.-f. Wong, Permeability evolution during localized deformation in Bentheim sandstone, J. Geophys. Res.,109, B10406, doi:10.1029/2003JB002942, 2004.

Paulsen, R. J., D. O�Rourke, C. F. Smith and T.-f. Wong, Tidal load and saltwater influences on submarine ground water discharge, Ground Water, 42, 990-999, 2004.

He, C., T.-f. Wong, and N. M. Beeler, Scaling of stress drop with recurrence interval and loading velocity for laboratory-derived fault strength relations, J. Geophys. Res., 108 (B1), 2037, doi:10.1029/ 2002JB001890, 2003.

Beeler, N. M., T.-f. Wong, and S. H. Hickman, On the expected relationships between apparent stress, static stress drop, effective shear fracture energy and seismic efficiency, Bull. Seism. Soc. Am ., 93, 1381-1389, 2003.

Paulsen, R. J., C. F. Smith, D. O'Rourke, and T.-f. Wong, Development and evaluation of an ultrasonic groundwater seepage meter, Ground Water, 39, 904-911, 2001.

Wong, T.-f., P. Baud, and E. Klein, Localized failure modes in a compactant porous rock, Geophys. Res. Lett., 28 , 2521-2524, 2001.

Lindquist, W. B., A. Venkatarangan, J. Dunsmuir, and T.-f. Wong, Pore and throat size distributions measured from synchrotron X-ray tomographic images of Fontainebleau sandstones, J. Geophys. Res ., 105, 21509-21527, 2000.

Ko, S.-c., D.L. Olgaard, and T.-f. Wong, Generation and maintenance of pore pressure excess in a dehydrating system, 1 Experimental and microstructural observations, J. Geophys. Res., 102 , 825-839, 1997.

Wong, T.-f., S.-c. Ko, and D.L. Olgaard, Generation and maintenance of pore pressure excess in a dehydrating system, 2 Theoretical analysis, J. Geophys. Res.,102, 841-852, 1997.

Wong, T.-f., C. David, and W. Zhu, The transition from brittle faulting to cataclastic flow in porous sandstones: Mechanical deformation, J. Geophys. Res., 102,3009-3025,1997.

Zhu, W., and T.-f. Wong, The transition from brittle faulting to cataclastic flow: Permeability evolution, J. Geophys. Res. ,102,3027-3041,1997.

Menendez, B., W. Zhu and T.-f. Wong, Micromechanics of brittle faulting and cataclastic flow in Berea sandstone, J. Struct. Geol., 18, 1-16, 1996.

Fredrich, J. T., B. Menendez and T.-f. Wong, Imaging the pore structure of geomaterials, Science, 268, 276-279, 1995.