The Dahuiyeh (Zarand) earthquake of 2005 February 22 in central Iran: reactivation of an intramountain reverse fault

We used seismic body waves, radar interferometry and field investigation to examine the source processes of the destructive earthquake of 2005 February 22 near Zarand, in south–central Iran. The earthquake ruptured an intramountain reverse fault, striking E–W and dipping north at ∼60° to a depth of about 10 km. It produced a series of coseismic scarps with up to 1 m vertical displacement over a total distance of ∼13 km, continuous for 7 km. The line of the coseismic ruptures followed a known geological fault of unknown, but probably pre-Late Cenozoic, age and involved bedding-plane slip where the scarps were continuous at the surface. However, any signs of earlier coseismic ruptures along this fault had been obliterated by the time of the 2005 earthquake, probably by land sliding and weathering, so that the fault could not reasonably have been identified as active beforehand. The 2005 fault is at an oblique angle to the range-bounding Kuh Banan strike-slip fault, and may represent a splay from that fault, related to its southern termination. Other intramountain reverse faulting earthquakes have occurred in Iran, but this is the first to have produced a clear, mapped surface rupture, and to have been studied with InSAR. Faults of this type represent a serious seismic hazard in Iran and are difficult to assess, because their geomorphological expression is much less clear than the range-bounding reverse faults, which are more common and have been better studied.

[1]  NábÄ lek,et al.  Determination of earthquake source parameters from inversion of body waves , 1984 .

[2]  James Jackson,et al.  Active tectonics of the north and central Aegean Sea , 1991 .

[3]  Frederic Masson,et al.  Present‐day crustal deformation and plate kinematics in the Middle East constrained by GPS measurements in Iran and northern Oman , 2004 .

[4]  C. Werner,et al.  Radar interferogram filtering for geophysical applications , 1998 .

[5]  Robert McCaffrey,et al.  SYN3: A Program for Inversion of Teleseismic Body Wave Forms on Microcomputers , 1988 .

[6]  James Jackson,et al.  Offset and evolution of the Gowk fault, S.E. Iran: a major intra-continental strike-slip system , 2002 .

[7]  J. Jackson,et al.  Active tectonics and late Cenozoic strain distribution in central and eastern Iran , 2004 .

[8]  H. Philip,et al.  Ruptures of Major Earthquakes and Active Deformation in Mongolia and Its Surroundings , 1993 .

[9]  J. Nábělek,et al.  Earthquakes, gravity, and the origin of the Bali Basin: An example of a Nascent Continental Fold-and-Thrust Belt , 1987 .

[10]  J. Jackson,et al.  Field examples of strike‐slip fault terminations in Mongolia and their tectonic significance , 1999 .

[11]  M. Berberian,et al.  Field and teleseismic observations of the 1981 Golbaf–Sirch earthquakes in SE Iran , 1984 .

[12]  E. B. M. M. Binasi.  Geological survey of Iran , 1975 .

[13]  P. Rosen,et al.  Updated repeat orbit interferometry package released , 2004 .

[14]  M. Berberian,et al.  Patterns of historical earthquake rupture in the Iranian Plateau , 1999, Bulletin of the Seismological Society of America.

[15]  H. Zebker,et al.  Fault Slip Distribution of the 1999 Mw 7.1 Hector Mine, California, Earthquake, Estimated from Satellite Radar and GPS Measurements , 2002 .

[16]  E. Engdahl,et al.  Global teleseismic earthquake relocation with improved travel times and procedures for depth determination , 1998, Bulletin of the Seismological Society of America.

[17]  T. Wright,et al.  Toward mapping surface deformation in three dimensions using InSAR , 2004 .

[18]  T. Wright,et al.  The 1998 March 14 Fandoqa earthquake (Mw 6.6) in Kerman province, southeast Iran: re‐rupture of the 1981 Sirch earthquake fault, triggering of slip on adjacent thrusts and the active tectonics of the Gowk fault zone , 2001 .

[19]  N. Ambraseys,et al.  A history of Persian earthquakes , 1982 .

[20]  James Jackson,et al.  The 2002 June 22 Changureh (Avaj) earthquake in Qazvin province, northwest Iran: epicentral relocation, source parameters, surface deformation and geomorphology , 2005 .

[21]  P. Molnar,et al.  Fault plane solutions of earthquakes and active tectonics of the Tibetan Plateau and its margins , 1989 .

[22]  K. Priestley,et al.  The 1994 Sefidabeh earthquakes in eastern Iran: blind thrusting and bedding‐plane slip on a growing anticline, and active tectonics of the Sistan suture zone , 2000 .

[23]  Peter J. Clarke,et al.  Source parameters of the 1 October 1995 Dinar (Turkey) earthquake from SAR interferometry and seismic bodywave modelling , 1999 .

[24]  Jim Mori,et al.  Overlapping fault planes of the 1971 San Fernando and 1994 Northridge, California earthquakes , 1995 .

[25]  Bertrand Meyer,et al.  Crustal thickening in Gansu‐Qinghai, lithospheric mantle subduction, and oblique, strike‐slip controlled growth of the Tibet plateau , 1998 .

[26]  R. Walker,et al.  The 22 June 2002 Changureh (Avaj) Earthquake in Qazvin Province, NW Iran: Epicentral Re-location, Source Parameters, Surface Deformation and Geomorphology. , 2004 .

[27]  T. Wright,et al.  The 2003 Bam (Iran) earthquake: Rupture of a blind strike‐slip fault , 2004 .

[28]  James Jackson,et al.  Surface expression of thrust faulting in eastern Iran: source parameters and surface deformation of the 1978 Tabas and 1968 Ferdows earthquake sequences , 2003 .

[29]  Ian Parsons,et al.  Surface deformation due to shear and tensile faults in a half-space , 1986 .

[30]  James Jackson,et al.  The continuity of active fault systems in Greece , 2001 .

[31]  M. Berberian,et al.  Surface rupture and mechanism of the Bob-Tangol (southeastern Iran) earthquake of 19 December 1977 , 1979 .