Crustal deformation and fault slip during the seismic cycle in the North Chile subduction zone, from GPS and InSAR observations

SUMMARY The different phases of the earthquake cycle can produce measurable deformation of the Earth's surface. This work is aimed at describing the evolution of that deformation in space and time, as well as the distribution of causal slip on the fault at depth. We have applied GPS and synthetic aperture radar (SAR) interferometry (InSAR) techniques to northern Chile, where fast plate convergence rates are associated with large subduction earthquakes and extensive crustal deformation. The region of northern Chile between 18°S and 23°S is one of the most important seismic gaps in the world, with no rupture having occurred since 1877. In 1995, the Mw= 8.1 Antofagasta earthquake ruptured the subduction interface over a length of 180 km in the region immediately to the south of this 450 km long gap. The coseismic deformation associated with this event has been documented previously. Here we use GPS position time-series for 40 benchmarks (measured between 1996 and 2000) and ERS SAR interferograms (for the interval between 1995 and 1999) to map both the post-seismic deformation following the 1995 event and the ongoing interseismic deformation in the adjacent gap region. In the seismic gap, the interseismic velocities of 20–30 mm yr−1 to the east with respect to South America are mapped. Both the GPS and the InSAR measurements can be modelled with 100 per cent coupling of the thrust interface of the subduction to a depth of 35 km, with a transition zone extending down to 55 km depth. The slip rate in that zone increases linearly from zero to the plate convergence rate. South of the gap, the interferometric map shows interseismic deformation superimposed with deformation following the 1995 earthquake and covering the same area as the coseismic deformation. Some 40 per cent of this deformation is related to seismic activity in the 3.3 yr following the 1995 event, in particular slip during a Mw= 7.1 earthquake in 1998. However, most of the signal (60 per cent) corresponds to post-seismic deformation resulting from widespread aseismic slip in the subduction interface. The afterslip appears to have occurred down-dip in the transition zone at 35–55 km depth and to have propagated laterally northwards at 25–45 km depth under the Mejillones Peninsula, which is a prominent geomorphological feature at the boundary between the 1877 and 1995 rupture zones. We propose a simple slip model for the seismic cycle associated with the Antofagasta earthquake, where the transition zone alternates between aseismic shear and seismic slip.

[1]  Bertrand Meyer,et al.  Coseismic and early post-seismic slip associated with the 1999 Izmit earthquake (Turkey), from SAR interferometry and tectonic field observations , 2003 .

[2]  Giorgi Khazaradze,et al.  Short‐ and long‐term effects of GPS measured crustal deformation rates along the south central Andes , 2003 .

[3]  Timothy Ian Melbourne,et al.  Rapid postseismic transients in subduction zones from continuous GPS , 2002 .

[4]  Paul A. Rosen,et al.  Co-seismic slip from the 1995 July 30 Mw= 8.1 Antofagasta, Chile, earthquake as constrained by InSAR and GPS observations , 2002 .

[5]  Timothy H. Dixon,et al.  REVEL: A model for Recent plate velocities from space geodesy , 2002 .

[6]  M. Wyss,et al.  Mapping spatial variability of the frequency-magnitude distribution of earthquakes , 2002 .

[7]  Detlef Angermann,et al.  Earthquake cycle dominates contemporary crustal deformation in Central and Southern Andes , 2001 .

[8]  R. Allmendinger,et al.  On the strength of interplate coupling and the rate of back arc convergence in the central Andes: An analysis of the interseismic velocity field , 2001 .

[9]  J. Ruegg,et al.  Co-, Post- and Pre(?)-seismic Displacements Associated with the Mw 8.4 Southern Peru Earthquake of 23 June 2001 from Continuous GPS Measurements , 2001 .

[10]  Paul A. Rosen,et al.  Transient strain accumulation and fault interaction in the eastern California shear zone , 2001 .

[11]  M. Bevis,et al.  An integrated crustal velocity field for the central Andes , 2001 .

[12]  K. Larson,et al.  Transient fault slip in Guerrero, southern Mexico , 2001 .

[13]  Jean-Philippe Avouac,et al.  On the use of dislocations to model interseismic strain and stress build-up at intracontinental thrust faults , 2001 .

[14]  J. Freymueller,et al.  Crustal uplift in the south central Alaska subduction zone: New analysis and interpretation of tide gauge observations , 2001 .

[15]  Kelin Wang,et al.  A Silent Slip Event on the Deeper Cascadia Subduction Interface , 2001, Science.

[16]  G. Bock,et al.  High‐resolution image of the oceanic moho in the subducting Nazca Plate from P‐S converted waves , 2000 .

[17]  Crustal motion north and south of the Arica deflection: Comparing recent geodetic results from the central Andes , 2000 .

[18]  Demitris Paradissis,et al.  Global Positioning System constraints on plate kinematics and dynamics in the eastern Mediterranean and Caucasus , 2000 .

[19]  M. Sobiesiak.  Fault plane structure of the Antofagasta, Chile Earthquake of 1995 , 2000 .

[20]  S. Miyazaki,et al.  A slow thrust slip event following the two 1996 Hyuganada Earthquakes beneath the Bungo Channel, southwest Japan , 1999 .

[21]  Detlef Angermann,et al.  Space-geodetic estimation of the nazca-south america euler vector , 1999 .

[22]  E. Kissling,et al.  Accurate hypocentre determination in the seismogenic zone of the subducting Nazca Plate in northern Chile using a combined on-/offshore network , 1999 .

[23]  Kelin Wang,et al.  The updip and downdip limits to great subduction earthquakes: Thermal and structural models of Casca , 1999 .

[24]  Detlef Angermann,et al.  GPS-derived Deformation of the Central Andes Including the 1995 Antofagasta Mw = 8.0 Earthquake , 1999 .

[25]  T. Lay,et al.  Rupture Process of the 1995 Antofagasta Subduction Earthquake (Mw = 8.1) , 1999 .

[26]  J. Mechie,et al.  Two‐dimensional velocity models of the Nazca Plate subduction zone between 19.5°S and 25°S from wide‐angle seismic measurements during the CINCA95 project , 1999 .

[27]  O. Oncken,et al.  Seismic reflection image revealing offset of Andean subduction-zone earthquake locations into oceanic mantle , 1999 .

[28]  Steven C. Cohen.  Numerical Models of Crustal Deformation in Seismic Zones , 1999 .

[29]  the Chicxulub Working Group.  Seismic reflection image revealing offset of Andean subduction-zone earthquake locations into oceanic mantle , 1999, Nature.

[30]  Walter H. F. Smith,et al.  New, improved version of generic mapping tools released , 1998 .

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

[32]  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.

[33]  P. Visser,et al.  Precise orbit determination and gravity field improvement for the ERS satellites , 1998 .

[34]  T. Dixon,et al.  Space geodetic observations of nazca-south america convergence across the central andes , 1998, Science.

[35]  J. Ruegg,et al.  Source tomography by simulated annealing using broad‐band surface waves and geodetic data: application to the Mw= 8.1 Chile 1995 event , 1997 .

[36]  J. Freymueller,et al.  Deformation of the Kenai Peninsula, Alaska , 1997 .

[37]  Tomowo Hirasawa,et al.  A numerical study on seismic coupling along subduction zones using a laboratory-derived friction law , 1997 .

[38]  L. Rivera,et al.  The Mw = 8.0 Antofagasta (northern Chile) earthquake of 30 July 1995: A precursor to the end of the large 1877 gap , 1997, Bulletin of the Seismological Society of America.

[39]  R. Armijo,et al.  The MW=8.1 Antofagasta (North Chile) Earthquake of July 30, 1995: First results from teleseismic and geodetic data , 1996 .

[40]  D. Comte,et al.  Stress distribution and geometry of the subducting Nazca plate in northern Chile using teleseismically recorded earthquakes , 1995 .

[41]  Richard G. Gordon,et al.  Effect of recent revisions to the geomagnetic reversal time scale on estimates of current plate motions , 1994 .

[42]  Kelin Wang,et al.  Current deformation and the width of the seismogenic zone of the northern Cascadia subduction thrust , 1994 .

[43]  K. Feigl,et al.  The displacement field of the Landers earthquake mapped by radar interferometry , 1993, Nature.

[44]  Kelin Wang,et al.  Thermal constraints on the zone of major thrust earthquake failure: The Cascadia Subduction Zone , 1993 .

[45]  Larry J. Ruff,et al.  Depth of seismic coupling along subduction zones , 1993 .

[46]  Richard G. Gordon,et al.  No-net-rotation model of current plate velocities incorporating plate motion model NUVEL-1 , 1991 .

[47]  L. Ruff,et al.  Seismic coupling along the Chilean Subduction Zone , 1991 .

[48]  Mario Pardo,et al.  Reappraisal of great historical earthquakes in the northern Chile and southern Peru seismic gaps , 1991 .

[49]  Stuart P. Nishenko,et al.  Circum-Pacific seismic potential: 1989–1999 , 1991 .

[50]  Ricardo Thiele,et al.  Active faulting in northern Chile: ramp stacking and lateral decoupling along a subduction plate boundary? , 1990 .

[51]  R. Goldstein,et al.  Mapping small elevation changes over large areas: Differential radar interferometry , 1989 .

[52]  C. Werner,et al.  Satellite radar interferometry: Two-dimensional phase unwrapping , 1988 .

[53]  William D. Stuart,et al.  Forecast model for great earthquakes at the Nankai Trough subduction zone , 1988 .

[54]  John R. Rice,et al.  Crustal Earthquake Instability in Relation to the Depth Variation of Frictional Slip Properties , 1986 .

[55]  Y. Okada.  Surface deformation due to shear and tensile faults in a half-space , 1985 .

[56]  Stuart P. Nishenko,et al.  Seismic potential for large and great interplate earthquakes along the Chilean and Southern Peruvian Margins of South America: A quantitative reappraisal , 1985 .

[57]  Kurt L. Feigl,et al.  Space geodetic measurement of crustal deformation in central and southern California , 1993 .

[58]  J. Rundle,et al.  A viscoelastic coupling model for the cyclic deformation due to periodically repeated Earthquakes at subduction zones , 1984 .

[59]  W. Thatcher.  The earthquake deformation cycle at the Nankai Trough, southwest Japan , 1984 .

[60]  J. C. Savage.  A dislocation model of strain accumulation and release at a subduction zone , 1983 .

[61]  John Kelleher,et al.  Rupture zones of large South American earthquakes and some predictions , 1972 .