Characterization of Source Parameters and Some Empirical Relations between Them for Kachchh Region, Gujarat, India: Implication of January 26, 2001 Bhuj Earthquake and Its Aftershock Sequence
Affiliation(s)
1 India Meteorological Department, Ahmedabad, India. 2 CSIR Fourth Paradigm Institute (Formerly C-MMACS), Bangalore, India.
1 India Meteorological Department, Ahmedabad, India. 2 CSIR Fourth Paradigm Institute (Formerly C-MMACS), Bangalore, India.
ABSTRACT
Study of source parameters of small to moderate and large earthquakes is important to understand the differences and similarities between dynamic ruptures of different earthquakes and clarifying the scaling relations. In the present study, we have characterized source parameters and presented new and revised empirical relationships between various source parameters for Kachchh region of Gujarat, India to facilitate to draw first-order conclusions regarding the trends in the region. We have studied total 202 aftershocks of shallow-focus (hypo central depth less than 40 km) and moderate magnitude recorded over the Kachchh region during January 2001 to December 2012 by different seismological observatories of India Meteorological Department. We have adopted the spectral technique for source parameter estimation, where S-wave displacement spectra are considered and applied Fast Fourier Transform (FFT) to compute displacement spectra. We have followed the Brune’s source model for our estimation and the estimated values of source parameters show close approximation to the global values. While derived empirical relations between different source parameters, they demonstrate direct or inverse proportion to linear or power scale. Interrelation between seismic moment, rupture parameters, corner frequency and radiated seismic energy can be summarized as
, 
, 
and ER μ M0 and ER μ Mw for our analysis. Stress
drop distribution over the Kachchh region is very scattered and due to its
peculiar behavior, it is difficult to derive its empirical relation with other
source parameters. Sufficient accuracy on measuring source parameters like
corner frequency stress drop, rupture dimensions, radiated seismic energy etc.
helps to understand earthquake processes in the region. This is the first ever
attempt to establish empirical relation between different source parameters for
Kachchh region for longer aftershock sequence and they are useful to assess
future earthquake potential over the region.
Study of source parameters of small to moderate and large earthquakes is important to understand the differences and similarities between dynamic ruptures of different earthquakes and clarifying the scaling relations. In the present study, we have characterized source parameters and presented new and revised empirical relationships between various source parameters for Kachchh region of Gujarat, India to facilitate to draw first-order conclusions regarding the trends in the region. We have studied total 202 aftershocks of shallow-focus (hypo central depth less than 40 km) and moderate magnitude recorded over the Kachchh region during January 2001 to December 2012 by different seismological observatories of India Meteorological Department. We have adopted the spectral technique for source parameter estimation, where S-wave displacement spectra are considered and applied Fast Fourier Transform (FFT) to compute displacement spectra. We have followed the Brune’s source model for our estimation and the estimated values of source parameters show close approximation to the global values. While derived empirical relations between different source parameters, they demonstrate direct or inverse proportion to linear or power scale. Interrelation between seismic moment, rupture parameters, corner frequency and radiated seismic energy can be summarized as
, , and ER μ M0 and ER μ Mw for our analysis. Stress
drop distribution over the Kachchh region is very scattered and due to its
peculiar behavior, it is difficult to derive its empirical relation with other
source parameters. Sufficient accuracy on measuring source parameters like
corner frequency stress drop, rupture dimensions, radiated seismic energy etc.
helps to understand earthquake processes in the region. This is the first ever
attempt to establish empirical relation between different source parameters for
Kachchh region for longer aftershock sequence and they are useful to assess
future earthquake potential over the region.
Cite this paper
Trivedi, P. C. and Parvez, I. A. (2015) Characterization of Source Parameters and Some Empirical Relations between Them for Kachchh Region, Gujarat, India: Implication of January 26, 2001 Bhuj Earthquake and Its Aftershock Sequence. International Journal of Geosciences, 6, 1127-1139. doi: 10.4236/ijg.2015.610088.
Trivedi, P. C. and Parvez, I. A. (2015) Characterization of Source Parameters and Some Empirical Relations between Them for Kachchh Region, Gujarat, India: Implication of January 26, 2001 Bhuj Earthquake and Its Aftershock Sequence. International Journal of Geosciences, 6, 1127-1139. doi: 10.4236/ijg.2015.610088.
References
[1] Darragh, R.B. and Bolt, B.A. (1987) A Comment on the Statistical Regression Relation between Earthquake Magnitude and Fault Rupture Length. Bulletin of the Seismological Society of America, 77, 1479-1484. [2] Kanamori, H. and Anderson, D.L. (1975) Theoretical Basis of Some Empirical Relations in Seismology. Bulletin of the Seismological Society of America, 65, 1073-1096. [3] Purcaru, G. and Berckhemer, H. (1982) Quantitative Relations of Seismic Source Parameters and a Classification of Earthquakes. In: Duda, S.J. and Aki, Eds., Quantification of Earthquakes, Tectonophysics, 84, 57-128. http://dx.doi.org/10.1016/0040-1951(82)90154-8 [4] Singh, S.K., Bazan, E. and Esteva, L. (1980) Expected Earthquake Magnitude from a Fault. Bulletin of the Seismological Society of America, 70, 903-914. [5] Brune, J. (1970) Tectonic Stress and the Spectra of Seismic Shear Waves from Earthquakes. Journal of Geophysical Research, 75, 4997-5009. http://dx.doi.org/10.1029/JB075i026p04997 [6] Herrmann, R.B. and Kijko, A. (1983) Modelling Some Empirical Vertical Component Kg Relations. Bulletin of the Seismological Society of America, 73, 157-171. [7] Singh, S.K., Apsel, R.J., Fried, J. and Brune, J.N. (1982) Spectral Attenuation of SH-Waves along the Imperial Fault. Bulletin of the Seismological Society of America, 72, 2003-2016. [8] Andrews, D.J. (1986) Objective Determination of Source Parameters and Similarity of Earthquakes of Different Size, Earthquake Source Mechanics. American Geophysical Union, Washington DC, 259-268. [9] Lermo, J. and Chavez-Garcia, F.J. (1993) Site Effect Evaluation Using Spectral Ratios with Only One Station. Bulletin of the Seismological Society of America, 83, 1574-1594. [10] Nath, S.K., Sengupta, P. and Kayal, J.R. (2002) Determination of Site Response at Garhwal Himalaya from the Aftershock Sequence of 1999 Chamoli Earthquake. Bulletin of the Seismological Society of America, 92, 1071-1081. http://dx.doi.org/10.1785/0120000246 [11] Nath, S.K., Biswas, N.N., Dravinski, M. and Papageorgiou, A. (2002) Determination of S-Wave Site Response in Anchorage, Alaska in the 1 - 9 Hz Frequency Band. Pure and Applied Geophysics, 159, 2673-2698. http://dx.doi.org/10.1007/s00024-002-8753-4 [12] Mandal, P. (2007) Sediment Thicknesses and Qs vs. Qp Relations in the Kachchh Rift Basin, Gujarat, India Using Sp Converted Phases. Pure and Applied Geophysics, 164, 135-160.
http://dx.doi.org/10.1007/s00024-006-0158-3 [13] Mandal, P. and Pujol, J. (2006) Seismic Imaging of the Aftershock Zone of the 2001 Mw 7.7 Bhuj Earthquake, India. Geophysical Research Letters, 33, Article ID: L05309. [14] Mandal, P., Jainendra, S., Joshi, S., Kumar, S., Bhunia, R. and Rastogi, B.K. (2004) Low Coda-Qc in the Epicentral Region of the 2001 Bhuj Earthquake of Mw 7.7. Pure and Applied Geophysics, 161, 1635-1654. http://dx.doi.org/10.1007/s00024-004-2525-2 [15] Aki, K. and Chouet, B. (1975) Origin of Coda Waves: Source, Attenuation and Scattering Effects. Journal of Geophysical Research, 80, 3322-3342. http://dx.doi.org/10.1029/jb080i023p03322 [16] Mandal, P., Chadha, R.K., Satyamurty, C., Raju, I.P. and Kumar, N. (2005) Estimation of Site Response in Kachchh, Gujarat, India, Region Using H = V Spectral Ratios of Aftershocks of the 2001 Mw 7.7 Bhuj Earthquake. Pure and Applied Geophysics, 162, 2479-2504. http://dx.doi.org/10.1007/s00024-005-2784-6 [17] Mandal, P., Dutta, U. and Chadha, R.K. (2008) Estimation of Site Response in the Kachchh Seismic Zone, Gujarat, India. Bulletin of the Seismological Society of America, 98, 2559-2566.
http://dx.doi.org/10.1785/0120070309 [18] Singh, S.K., Pacheco, J.F., Bansal, B.K., Perez-Campos, X., Dattatrayam, R.S. and Suresh, G. (2004) A Source Study of the Bhuj, India, Earthquake of 26 January 2001 (Mw 7.6). Bulletin of the Seismological Society of America, 94, 1195-1206. http://dx.doi.org/10.1785/012003212 [19] Bodin, P. and Horton, S. (2004) Source Parameters and Tectonic Implications of Aftershocks of the Mw 7.6 Bhuj Earthquake of Bhuj Earthquake of January 26, 2001. Bulletin of the Seismological Society of America, 94, 818-827. http://dx.doi.org/10.1785/0120030176 [20] Hanks, T.C. and Kanamori, H. (1979) A Moment-Magnitude Scale. Journal of Geophysical Research, 84, 2348-2350. http://dx.doi.org/10.1029/JB084iB05p02348 [21] Ben-Menahem, A., Smith, S.W. and Teng, T.L. (1965) A Procedure for Source Studies from Spectrums of Long Period Seismic Body Waves. Bulletin of the Seismological Society of America, 55, 203-235. [22] Keilis-Borok, V.I. (1959) An Estimation of the Displacement in an Earthquake Source and of Source Dimensions. Annali di Geofisica, 12, 205-214. [23] Richter, C.F. (1958) Elementary Seismology. W.H. Freeman, San Francisco, 768. [24] Archileta, R.J., Cranswick, E., Muellar, C. and Spudich, P. (1982) Source Parameters of the 1980 Mammoth Lakes, California, Earthquake Sequence. Journal of Geophysical Research, 87, 4595-4607.
http://dx.doi.org/10.1029/JB087iB06p04595 [25] Hanks, T.C., Hileman, J.A. and Thatcher, W. (1975) Seismic Moment of Larger Earthquakes of the Southern California Region. Geological Society of America Bulletin, 86, 1131-1139.
http://dx.doi.org/10.1130/0016-7606(1975)86<1131:SMOTLE>2.0.CO;2 [26] Izutani, Y. (2005) Radiated Seismic Energy from the Mid Niigata, Japan, Earthquake of October 23, 2004 and Its Aftershocks. Geophysical Research Letters, 32, Article ID: L21313.
http://dx.doi.org/10.1029/2005GL024116 [27] Mayeda, K.M., Yoo, S., Walter, W.R., G?k, R.M. and Malagnini, L. (2012) Improved High Frequency Discrimination: A New Approach to Correct for Regional Source Scaling Variations. 2012 Monitoring Research Review: Ground-Based Nuclear Explosion Monitoring Technologies, 453-458. [28] Kanamori, H. and Rivera, L. (2004) Static and Dynamic Scaling Relations for Earthquake and Their Implications for Rupture Speed and Stress Drop. Bulletin of the Seismological Society of America, 94, 314-319. http://dx.doi.org/10.1785/0120030159 [29] Walter, W.R., Mayeda, K. and Patton, H. (1995) Phase and Spectral Ratio Discrimination between NTS Earthquakes and Explosions, Part I: Empirical Observations. Bulletin of the Seismological Society of America, 85, 1050-1067. [30] Abe, K. (1975) Determination of Static and Dynamic Fault Parameters of the Saitama Earthquake of July, 1968. Tectonophysics, 27, 223-238. http://dx.doi.org/10.1016/0040-1951(75)90018-9 [31] Abercrombie, R. (1995) Earthquake Source Scaling Relationships from ?1 to 5 ML Using Seismograms Recorded at 2.5-km Depth. Journal of Geophysical Research, 100, 15-24.
http://dx.doi.org/10.1029/95JB02397 [32] Boatwright, J. and Choy, G.L. (1986) Teleseismic Estimates of the Energy Radiated by Shallow Earthquakes. Journal of Geophysical Research, 91, 2095-2112.
http://dx.doi.org/10.1029/JB091iB02p02095 [33] Choy, G.L. and Botwright, J.L. (2012) Radiated Seismic Energy and Energy Magnitude. In: Bormann, P., Ed., New Manual of Seismological Observatory Practice (NMSOP-2), IASPEI, GFZ German Research Centre for Geosciences, Potsdam, 1-9. [34] Gutenberg, B. and Richter, C.F. (1956) Earthquake Magnitude, Intensity, Energy and Acceleration. Bulletin of the Seismological Society of America, 46, 105-145. [35] Choy, G.L. and Boatwright, J.L. (1995) Global Patterns of Radiated Seismic Energy and Apparent Stress. Journal of Geophysical Research, 100, 18205-18228. http://dx.doi.org/10.1029/95JB01969 [36] Ide, S., Beroza, G., Prejean, S. and Ellsworth, W. (2003) Apparent Break in Earthquake Scaling Due to Path and Site Effects in Deep Borehole Recordings. Journal of Geophysical Research, 108, 2271. http://dx.doi.org/10.1029/2001jb001617 [37] Allmann, B.P. and Shearer, P.M. (2009) Global Variations of Stress Drop for Moderate to Large Earthquakes. Journal of Geophysical Research, 114, Article ID: B01310. [38] Prieto, G.A., Thomson, D., Vernon, F., Shearer, P. and Parker, R. (2007) Confidence Intervals for Earthquake Source Parameters. Geophysical Journal International, 168, 1227-1234.
http://dx.doi.org/10.1111/j.1365-246X.2006.03257.x [39] Sonley, E. and Abercrombie, R.E. (2006) Effects of Methods of Attenuation Correction on Source Parameter Determination. In: Abercrombie, R., Ed., Earthquakes: Radiated Seismic Energy and the Physics of Faulting, AGU, Washington DC, 91-97. http://dx.doi.org/10.1029/170GM11 [40] Mandal, P., Rastogi, B.K., Satyanarayan, H.V.S. and Kousalya, M. (2004) Results from Local Earthquake Velocity Tomography: Implications toward the Source Process Involved in Generating the 2001 Bhuj Earthquake in the Lower Cruts Beneath Kachchh (India). Bulletin of the Seismological Society of America, 94, 633-649. http://dx.doi.org/10.1785/0120030056 [41] Rice, J.R. (1990) Fault Stress States, Pore Pressure Distributions and the Weakness of the San Andreas Fault (Abstract). Eos, Transactions American Geophysical Union, 71, 1652.
[1] Darragh, R.B. and Bolt, B.A. (1987) A Comment on the Statistical Regression Relation between Earthquake Magnitude and Fault Rupture Length. Bulletin of the Seismological Society of America, 77, 1479-1484. [2] Kanamori, H. and Anderson, D.L. (1975) Theoretical Basis of Some Empirical Relations in Seismology. Bulletin of the Seismological Society of America, 65, 1073-1096. [3] Purcaru, G. and Berckhemer, H. (1982) Quantitative Relations of Seismic Source Parameters and a Classification of Earthquakes. In: Duda, S.J. and Aki, Eds., Quantification of Earthquakes, Tectonophysics, 84, 57-128. http://dx.doi.org/10.1016/0040-1951(82)90154-8 [4] Singh, S.K., Bazan, E. and Esteva, L. (1980) Expected Earthquake Magnitude from a Fault. Bulletin of the Seismological Society of America, 70, 903-914. [5] Brune, J. (1970) Tectonic Stress and the Spectra of Seismic Shear Waves from Earthquakes. Journal of Geophysical Research, 75, 4997-5009. http://dx.doi.org/10.1029/JB075i026p04997 [6] Herrmann, R.B. and Kijko, A. (1983) Modelling Some Empirical Vertical Component Kg Relations. Bulletin of the Seismological Society of America, 73, 157-171. [7] Singh, S.K., Apsel, R.J., Fried, J. and Brune, J.N. (1982) Spectral Attenuation of SH-Waves along the Imperial Fault. Bulletin of the Seismological Society of America, 72, 2003-2016. [8] Andrews, D.J. (1986) Objective Determination of Source Parameters and Similarity of Earthquakes of Different Size, Earthquake Source Mechanics. American Geophysical Union, Washington DC, 259-268. [9] Lermo, J. and Chavez-Garcia, F.J. (1993) Site Effect Evaluation Using Spectral Ratios with Only One Station. Bulletin of the Seismological Society of America, 83, 1574-1594. [10] Nath, S.K., Sengupta, P. and Kayal, J.R. (2002) Determination of Site Response at Garhwal Himalaya from the Aftershock Sequence of 1999 Chamoli Earthquake. Bulletin of the Seismological Society of America, 92, 1071-1081. http://dx.doi.org/10.1785/0120000246 [11] Nath, S.K., Biswas, N.N., Dravinski, M. and Papageorgiou, A. (2002) Determination of S-Wave Site Response in Anchorage, Alaska in the 1 - 9 Hz Frequency Band. Pure and Applied Geophysics, 159, 2673-2698. http://dx.doi.org/10.1007/s00024-002-8753-4 [12] Mandal, P. (2007) Sediment Thicknesses and Qs vs. Qp Relations in the Kachchh Rift Basin, Gujarat, India Using Sp Converted Phases. Pure and Applied Geophysics, 164, 135-160.
http://dx.doi.org/10.1007/s00024-006-0158-3 [13] Mandal, P. and Pujol, J. (2006) Seismic Imaging of the Aftershock Zone of the 2001 Mw 7.7 Bhuj Earthquake, India. Geophysical Research Letters, 33, Article ID: L05309. [14] Mandal, P., Jainendra, S., Joshi, S., Kumar, S., Bhunia, R. and Rastogi, B.K. (2004) Low Coda-Qc in the Epicentral Region of the 2001 Bhuj Earthquake of Mw 7.7. Pure and Applied Geophysics, 161, 1635-1654. http://dx.doi.org/10.1007/s00024-004-2525-2 [15] Aki, K. and Chouet, B. (1975) Origin of Coda Waves: Source, Attenuation and Scattering Effects. Journal of Geophysical Research, 80, 3322-3342. http://dx.doi.org/10.1029/jb080i023p03322 [16] Mandal, P., Chadha, R.K., Satyamurty, C., Raju, I.P. and Kumar, N. (2005) Estimation of Site Response in Kachchh, Gujarat, India, Region Using H = V Spectral Ratios of Aftershocks of the 2001 Mw 7.7 Bhuj Earthquake. Pure and Applied Geophysics, 162, 2479-2504. http://dx.doi.org/10.1007/s00024-005-2784-6 [17] Mandal, P., Dutta, U. and Chadha, R.K. (2008) Estimation of Site Response in the Kachchh Seismic Zone, Gujarat, India. Bulletin of the Seismological Society of America, 98, 2559-2566.
http://dx.doi.org/10.1785/0120070309 [18] Singh, S.K., Pacheco, J.F., Bansal, B.K., Perez-Campos, X., Dattatrayam, R.S. and Suresh, G. (2004) A Source Study of the Bhuj, India, Earthquake of 26 January 2001 (Mw 7.6). Bulletin of the Seismological Society of America, 94, 1195-1206. http://dx.doi.org/10.1785/012003212 [19] Bodin, P. and Horton, S. (2004) Source Parameters and Tectonic Implications of Aftershocks of the Mw 7.6 Bhuj Earthquake of Bhuj Earthquake of January 26, 2001. Bulletin of the Seismological Society of America, 94, 818-827. http://dx.doi.org/10.1785/0120030176 [20] Hanks, T.C. and Kanamori, H. (1979) A Moment-Magnitude Scale. Journal of Geophysical Research, 84, 2348-2350. http://dx.doi.org/10.1029/JB084iB05p02348 [21] Ben-Menahem, A., Smith, S.W. and Teng, T.L. (1965) A Procedure for Source Studies from Spectrums of Long Period Seismic Body Waves. Bulletin of the Seismological Society of America, 55, 203-235. [22] Keilis-Borok, V.I. (1959) An Estimation of the Displacement in an Earthquake Source and of Source Dimensions. Annali di Geofisica, 12, 205-214. [23] Richter, C.F. (1958) Elementary Seismology. W.H. Freeman, San Francisco, 768. [24] Archileta, R.J., Cranswick, E., Muellar, C. and Spudich, P. (1982) Source Parameters of the 1980 Mammoth Lakes, California, Earthquake Sequence. Journal of Geophysical Research, 87, 4595-4607.
http://dx.doi.org/10.1029/JB087iB06p04595 [25] Hanks, T.C., Hileman, J.A. and Thatcher, W. (1975) Seismic Moment of Larger Earthquakes of the Southern California Region. Geological Society of America Bulletin, 86, 1131-1139.
http://dx.doi.org/10.1130/0016-7606(1975)86<1131:SMOTLE>2.0.CO;2 [26] Izutani, Y. (2005) Radiated Seismic Energy from the Mid Niigata, Japan, Earthquake of October 23, 2004 and Its Aftershocks. Geophysical Research Letters, 32, Article ID: L21313.
http://dx.doi.org/10.1029/2005GL024116 [27] Mayeda, K.M., Yoo, S., Walter, W.R., G?k, R.M. and Malagnini, L. (2012) Improved High Frequency Discrimination: A New Approach to Correct for Regional Source Scaling Variations. 2012 Monitoring Research Review: Ground-Based Nuclear Explosion Monitoring Technologies, 453-458. [28] Kanamori, H. and Rivera, L. (2004) Static and Dynamic Scaling Relations for Earthquake and Their Implications for Rupture Speed and Stress Drop. Bulletin of the Seismological Society of America, 94, 314-319. http://dx.doi.org/10.1785/0120030159 [29] Walter, W.R., Mayeda, K. and Patton, H. (1995) Phase and Spectral Ratio Discrimination between NTS Earthquakes and Explosions, Part I: Empirical Observations. Bulletin of the Seismological Society of America, 85, 1050-1067. [30] Abe, K. (1975) Determination of Static and Dynamic Fault Parameters of the Saitama Earthquake of July, 1968. Tectonophysics, 27, 223-238. http://dx.doi.org/10.1016/0040-1951(75)90018-9 [31] Abercrombie, R. (1995) Earthquake Source Scaling Relationships from ?1 to 5 ML Using Seismograms Recorded at 2.5-km Depth. Journal of Geophysical Research, 100, 15-24.
http://dx.doi.org/10.1029/95JB02397 [32] Boatwright, J. and Choy, G.L. (1986) Teleseismic Estimates of the Energy Radiated by Shallow Earthquakes. Journal of Geophysical Research, 91, 2095-2112.
http://dx.doi.org/10.1029/JB091iB02p02095 [33] Choy, G.L. and Botwright, J.L. (2012) Radiated Seismic Energy and Energy Magnitude. In: Bormann, P., Ed., New Manual of Seismological Observatory Practice (NMSOP-2), IASPEI, GFZ German Research Centre for Geosciences, Potsdam, 1-9. [34] Gutenberg, B. and Richter, C.F. (1956) Earthquake Magnitude, Intensity, Energy and Acceleration. Bulletin of the Seismological Society of America, 46, 105-145. [35] Choy, G.L. and Boatwright, J.L. (1995) Global Patterns of Radiated Seismic Energy and Apparent Stress. Journal of Geophysical Research, 100, 18205-18228. http://dx.doi.org/10.1029/95JB01969 [36] Ide, S., Beroza, G., Prejean, S. and Ellsworth, W. (2003) Apparent Break in Earthquake Scaling Due to Path and Site Effects in Deep Borehole Recordings. Journal of Geophysical Research, 108, 2271. http://dx.doi.org/10.1029/2001jb001617 [37] Allmann, B.P. and Shearer, P.M. (2009) Global Variations of Stress Drop for Moderate to Large Earthquakes. Journal of Geophysical Research, 114, Article ID: B01310. [38] Prieto, G.A., Thomson, D., Vernon, F., Shearer, P. and Parker, R. (2007) Confidence Intervals for Earthquake Source Parameters. Geophysical Journal International, 168, 1227-1234.
http://dx.doi.org/10.1111/j.1365-246X.2006.03257.x [39] Sonley, E. and Abercrombie, R.E. (2006) Effects of Methods of Attenuation Correction on Source Parameter Determination. In: Abercrombie, R., Ed., Earthquakes: Radiated Seismic Energy and the Physics of Faulting, AGU, Washington DC, 91-97. http://dx.doi.org/10.1029/170GM11 [40] Mandal, P., Rastogi, B.K., Satyanarayan, H.V.S. and Kousalya, M. (2004) Results from Local Earthquake Velocity Tomography: Implications toward the Source Process Involved in Generating the 2001 Bhuj Earthquake in the Lower Cruts Beneath Kachchh (India). Bulletin of the Seismological Society of America, 94, 633-649. http://dx.doi.org/10.1785/0120030056 [41] Rice, J.R. (1990) Fault Stress States, Pore Pressure Distributions and the Weakness of the San Andreas Fault (Abstract). Eos, Transactions American Geophysical Union, 71, 1652.