Fault slip distribution of two June 2000 M W 6.5 earthquakes in South Iceland estimated from joint inversion of InSAR and GPS measurements

Abstract We present the first detailed estimates of co-seismic slip distribution on faults in the South Iceland Seismic Zone (SISZ), an area of bookshelf tectonics. We have estimated source parameters for two M W 6.5 earthquakes in the SISZ on June 17 and 21, 2000 through a joint inversion of InSAR and GPS measurements. Our preferred model indicates two simple 15 km long, near vertical faults extending from the surface to approximately 10 km depth. The geometry is in good agreement with the aftershock distribution. The dislocations experienced pure right-lateral strike-slip, reaching maxima of 2.6 m and 2.9 m for the June 17 and 21 events, respectively. We find that the distribution of slip with depth may be correlated to crustal layering, with more than 80% of the total geometric moment release occurring in the uppermost 6 km. According to the distributed slip model the middle and upper crust appears to be more apt to generate large displacements than the lower crust. The geodetic estimates of seismic moments are 4.4×10 18 Nm ( M W 6.4) and 5.0×10 18 Nm ( M W 6.5). The total moment released by the two events equals that generated by several decades of plate motion in the area, but is only a fraction of the moment accumulated in the area since the last major earthquake in 1912.

[1]  L. Rivera,et al.  Coseismic Deformation from the 1999 Mw 7.1 Hector Mine, California, Earthquake as Inferred from InSAR and GPS Observations , 2002 .

[2]  P. Segall,et al.  Detection of a locked zone at depth on the Parkfield, California, segment of the San Andreas Fault , 1987 .

[3]  K. Feigl,et al.  Radar interferometry and its application to changes in the Earth's surface , 1998 .

[4]  Ruth A. Harris,et al.  Introduction to Special Section: Stress Triggers, Stress Shadows, and Implications for Seismic Hazard , 1998 .

[5]  Paul Segall,et al.  Estimating source parameters from deformation data, with an application to the March 1997 earthquake swarm off the Izu Peninsula, Japan , 2001 .

[6]  F. Sigmundsson,et al.  Rift‐transform kinematics in south Iceland: Deformation from Global Positioning System measurements, 1986 to 1992 , 1995 .

[7]  Paul Segall,et al.  Post-earthquake ground movements correlated to pore-pressure transients , 2003, Nature.

[8]  Páll Einarsson,et al.  Styles of surface rupture accompanying the June 17 and 21, 2000 earthquakes in the South Iceland Seismic Zone , 2005 .

[9]  W. Menke,et al.  Tomographic image of the Mid‐Atlantic Plate Boundary in southwestern Iceland , 1993 .

[10]  Jens Havskov,et al.  Earthquake prediction research in the South Iceland seismic zone and the SIL project , 1993 .

[11]  C. Scholz,et al.  The 1912 Iceland earthquake rupture: Growth and development of a nascent transform system , 1993 .

[12]  Michael Heinert,et al.  Crustal deformation measured by GPS in the South Iceland Seismic Zone due to two large earthquakes in June 2000 , 2001 .

[13]  R. Cattin,et al.  Effects of superficial layers on coseismic displacements for a dip-slip fault and geophysical implications , 1999 .

[14]  S. Jónsson,et al.  Modeling volcano and earthquake deformation from satellite radar interferometric observations , 2002 .

[15]  P. Einarsson.  Earthquakes and present-day tectonism in Iceland , 1991 .

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

[17]  Michel Campillo,et al.  Contribution of radar interferometry to a two-step inversion of the kinematic process of the 1992 Landers earthquake , 1999 .

[18]  S. Welstead.  Fractal and Wavelet Image Compression Techniques , 1999 .

[19]  Charles L. Lawson,et al.  Solving least squares problems , 1976, Classics in applied mathematics.

[20]  Freysteinn Sigmundsson,et al.  Unwrapping ground displacement signals in satellite radar interferograms with aid of GPS data and MRF regularization , 2002, IEEE Trans. Geosci. Remote. Sens..

[21]  K. Ágústsson,et al.  Strain changes for the 1987 Vatnafjöll earthquake in south Iceland and possible magmatic triggering , 1999 .

[22]  Howard A. Zebker,et al.  Phase unwrapping algorithms for radar interferometry: residue-cut, least-squares, and synthesis algorithms , 1998 .

[23]  G. Pálmason.  Crustal structure of Iceland from explosion seismology , 1971 .

[24]  P. Einarsson,et al.  Distance changes in the South Iceland Seismic Zone 1977–1984 , 1989, Jökull.

[25]  A. Dziewoński,et al.  Centroid-moment tensor solutions for April–June 2000 , 2001 .

[26]  Freysteinn Sigmundsson,et al.  Crustal deformation near Hengill volcano, Iceland 1993–1998: Coupling between magmatic activity and faulting inferred from elastic modeling of satellite radar interferograms , 2000 .

[27]  Freysteinn Sigmundsson,et al.  Triggered fault slip on June 17, 2000 on the Reykjanes Peninsula, SW‐Iceland captured by radar interferometry , 2003 .

[28]  K. Gunnarsson,et al.  Seismic crustal structure in Iceland and surrounding area , 1991 .

[29]  S. Jónsson,et al.  Coulomb stress changes in the South Iceland Seismic Zone due to two large earthquakes in June 2000 , 2003 .

[30]  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 .

[31]  Herbert F. Wang.  Theory of Linear Poroelasticity with Applications to Geomechanics and Hydrogeology , 2000 .

[32]  G. G. Stokes.  "J." , 1890, The New Yale Book of Quotations.

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

[34]  K. Feigl,et al.  Coseismic interferograms of two MS=6.6 earthquakes in the South Iceland Seismic Zone, June 2000 , 2001 .

[35]  W. Menke,et al.  Cold crust in a hot spot , 1994 .

[36]  A. Dziewoński,et al.  Centroid-moment tensor solutions for April-June, 1997 , 1999 .

[37]  W. J. Morgan,et al.  Plume‐driven plumbing and crustal formation in Iceland , 2002 .

[38]  P. Einarsson,et al.  Earthquake fractures in the districts Land and Rangárvellir in the South Iceland seismic zone (Jarðskjálftasprungur á Landi og Rangárvöllum) , 1982, Jökull.