Rapid changes in the electrical state of the 1999 Izmit earthquake rupture zone

Crustal fluids exist near fault zones, but their relation to the processes that generate earthquakes, including slow-slip events, is unclear. Fault-zone fluids are characterized by low electrical resistivity. Here we investigate the time-dependent crustal resistivity in the rupture area of the 1999 Mw 7.6 Izmit earthquake using electromagnetic data acquired at four sites before and after the earthquake. Most estimates of apparent resistivity in the frequency range of 0.05 to 2.0 Hz show abrupt co-seismic decreases on the order of tens of per cent. Data acquired at two sites 1 month after the Izmit earthquake indicate that the resistivity had already returned to pre-seismic levels. We interpret such changes as the pressure-induced transition between isolated and interconnected fluids. Some data show pre-seismic changes and this suggests that the transition is associated with foreshocks and slow-slip events before large earthquakes.

[1]  Gary D. Egbert,et al.  High‐resolution electromagnetic imaging of the San Andreas Fault in central California , 1999 .

[2]  A. Marotta,et al.  Advances in Interpretation of Geological Processes: Refinement of Multi-scale Data and Integration in Numerical Modelling , 2010 .

[3]  Mustafa Aktar,et al.  The 1999 İzmit Earthquake Sequence in Turkey: Seismological and Tectonic Aspects , 2002 .

[4]  Semih Ergintav,et al.  Bulletin of the Seismological Society of America , 2002 .

[5]  Nikolaus von Bargen,et al.  Permeabilities, interfacial areas and curvatures of partially molten systems: Results of numerical computations of equilibrium microstructures , 1986 .

[6]  T. Goto,et al.  Resistivity structure of a seismic gap along the Atotsugawa Fault, Japan , 2005 .

[7]  Yoshimori Honkura,et al.  Magnetotelluric imaging of fluids in intraplate earthquake zones, NE Japan Back Arc , 2001 .

[8]  P. A. Bedrosiana,et al.  Geophysical images of the creeping segment of the San Andreas fault : implications for the role of crustal fluids in the earthquake process , 2004 .

[9]  R. C. Bailey,et al.  Decomposition of magnetotelluric impedance tensors in the presence of local three-dimensional galvanic distortion , 1989 .

[10]  S. Shtrikman,et al.  On some variational principles in anisotropic and nonhomogeneous elasticity , 1962 .

[11]  Gary D. Egbert,et al.  Internal structure of the San Andreas fault at Parkfield, California , 1997 .

[12]  A. Gürer,et al.  Relation between electrical resistivity and earthquake generation in the crust of West Anatolia, Turkey , 2007 .

[13]  M. Matsushima,et al.  Magnetotelluric imaging of the fault rupture area of the 1999 Izmit (Turkey) earthquake , 2005 .

[14]  Paul A. Bedrosian,et al.  A deep crustal fluid channel into the San Andreas Fault system near Parkfield, California , 2008 .

[15]  P. Bedrosian,et al.  Electrical resistivity structure at the SAFOD site from magnetotelluric exploration , 2004 .

[16]  E. Watson,et al.  Fluids in the lithosphere, 1. Experimentally-determined wetting characteristics of CO2H2O fluids and their implications for fluid transport, host-rock physical properties, and fluid inclusion formation , 1987 .

[17]  Yoshimori Honkura,et al.  A model for observed circular polarized electric fields coincident with the passage of large seismic waves , 2009 .

[18]  M. Matsushima,et al.  Preliminary results of multidisciplinary observations before, during and after the Kocaeli (Izmit) earthquake in the western part of the North Anatolian Fault Zone , 2000 .

[19]  A. Hoffmann-Rothe,et al.  Correlation of electrical conductivity and structural damage at a major strike-slip fault in northern Chile , 2004 .

[20]  Yasuo Ogawa,et al.  A two-dimensional magnetotelluric inversion assuming Gaussian static shift , 1995 .

[21]  Semih Ergintav,et al.  Time-Dependent Distributed Afterslip on and Deep below the İzmit Earthquake Rupture , 2002 .

[22]  Naoshi Hirata,et al.  Propagation of Slow Slip Leading Up to the 2011 Mw 9.0 Tohoku-Oki Earthquake , 2012, Science.

[23]  R. Sibson.  An episode of fault-valve behaviour during compressional inversion? — The 2004 MJ6.8 Mid-Niigata Prefecture, Japan, earthquake sequence , 2007 .

[24]  Magnetotelluric transect across the Niigata‐Kobe Tectonic Zone, central Japan: A clear correlation between strain accumulation and resistivity structure , 2009 .

[25]  C H Scholz,et al.  Earthquake prediction: a physical basis. , 1973, Science.

[26]  D. Tarling.  The physical basis , 1983 .

[27]  Ute Weckmann,et al.  Correlation between deep fluids, tremor and creep along the central San Andreas fault , 2011, Nature.

[28]  A. Hasegawa,et al.  Aftershock Activity of the 1999 İzmit, Turkey, Earthquake Revealed from Microearthquake Observations , 2002 .

[29]  M. Matsushima,et al.  Electrical characterization of the North Anatolian Fault Zone underneath the Marmara Sea, Turkey by ocean bottom magnetotellurics , 2013 .

[30]  M. Matsushima,et al.  Seismoelectromagnetic Effect Associated with the İzmit Earthquake and Its Aftershocks , 2002 .

[31]  M. Matsushima,et al.  Resistivity structure in the western part of the fault rupture zone associated with the 1999 İzmit earthquake and its seismogenic implication , 2003 .

[32]  P. Bedrosian,et al.  On the geoelectric structure of major strike-slip faults and shear zones , 2004 .

[33]  Y. Fujinawa,et al.  Seismotectonics in convergent plate boundary , 2002 .

[34]  T. Yoshino,et al.  Wetting properties of anorthite aggregates: Implications for fluid connectivity in continental lower crust , 2002 .

[35]  R. Mackie,et al.  A magnetotelluric investigation of the San Andreas Fault at Carrizo Plain, California , 1997 .

[36]  Y. Ogawa,et al.  Mid-crustal electrical conductors and their correlations to seismicity and deformation at Itoigawa-Shizuoka Tectonic Line, Central Japan , 2004 .

[37]  R. Sibson.  Rupturing in overpressured crust during compressional inversion—the case from NE Honshu, Japan , 2009 .

[38]  J. Nakajima,et al.  Deep structure of the northeastern Japan arc and its implications for crustal deformation and shallow seismic activity , 2005 .

[39]  S. Takakura,et al.  Resistivity structure across Itoigawa-Shizuoka tectonic line and its implications for concentrated deformation , 2002 .

[40]  Mustafa Aktar,et al.  Extended Nucleation of the 1999 Mw 7.6 Izmit Earthquake , 2011, Science.

[41]  Y. Mitsuhata,et al.  Electromagnetic heterogeneity of the seismogenic region of 1962 M6.5 Northern Miyagi Earthquake, northeastern Japan , 2001 .

[42]  Y. Honkura.  Partial melting and electrical conductivity anomalies beneath the Japan and Philippine seas , 1975 .

[43]  M. Becken,et al.  Magnetotelluric Studies at the San Andreas Fault Zone: Implications for the Role of Fluids , 2011, Surveys in Geophysics.

[44]  Gary D. Egbert,et al.  Along strike variations in the electrical structure of the San Andreas Fault at Parkfield, California , 2000 .