A revised dislocation model of interseismic deformation of the Cascadia subduction zone

[1] CAS3D-2, a new three-dimensional (3-D) dislocation model, is developed to model interseismic deformation rates at the Cascadia subduction zone. The model is considered a snapshot description of the deformation field that changes with time. The effect of northward secular motion of the central and southern Cascadia forearc sliver is subtracted to obtain the effective convergence between the subducting plate and the forearc. Horizontal deformation data, including strain rates and surface velocities from Global Positioning System (GPS) measurements, provide primary geodetic constraints, but uplift rate data from tide gauges and leveling also provide important validations for the model. A locked zone, based on the results of previous thermal models constrained by heat flow observations, is located entirely offshore beneath the continental slope. Similar to previous dislocation models, an effective zone of downdip transition from locking to full slip is used, but the slip deficit rate is assumed to decrease exponentially with downdip distance. The exponential function resolves the problem of overpredicting coastal GPS velocities and underpredicting inland velocities by previous models that used a linear downdip transition. A wide effective transition zone (ETZ) partially accounts for stress relaxation in the mantle wedge that cannot be simulated by the elastic model. The pattern of coseismic deformation is expected to be different from that of interseismic deformation at present, 300 years after the last great subduction earthquake. The downdip transition from full rupture to no slip should take place over a much narrower zone.

[1]  Toshinori Sato,et al.  Cyclic crustal movement, steady uplift of marine terraces, and evolution of the island arc-trench system in southwest Japan , 1992 .

[2]  K. Walker,et al.  Tidal marsh stratigraphy, sea-level change and large earthquakes, i: a 5000 year record in washington, U.S.A.☆ , 1996 .

[3]  Meghan S. Miller,et al.  Present‐day motion of the Sierra Nevada block and some tectonic implications for the Basin and Range province, North American Cordillera , 2000 .

[4]  K. Miyashita.  A MODEL OF PLATE CONVERGENCE IN SOUTHWEST JAPAN, INFERRED FROM LEVELING DATA ASSOCIATED WITH THE 1946 NANKAIDO EARTHQUAKE , 1987 .

[5]  Richard G. Gordon,et al.  Current plate motions , 1990 .

[6]  D. Argus,et al.  Current Sierra Nevada-North America motion from very long baseline interferometry:Implications for the kinematics of the western United States , 1991 .

[7]  J. Clague,et al.  History and isostatic effects of the last ice sheet in southern British Columbia , 2002 .

[8]  K. Satake,et al.  Coseismic slip distribution of the 1946 Nankai earthquake and aseismic slips caused by the earthquake , 2001 .

[9]  Kelin Wang.  Coupling of tectonic loading and earthquake fault slips at subduction zones , 1995 .

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

[11]  Deformation across the forearc of the Cascadia subduction zone at Cape Blanco, Oregon , 2000 .

[12]  T. Dixon,et al.  New kinematic models for Pacific‐North America motion from 3 Ma to present, I: Evidence for steady motion and biases in the NUVEL‐1A Model , 1999 .

[13]  J. Clague,et al.  Tsunamis and tectonic deformation at the northern Cascadia margin: a 3000-year record from Deserted Lake, Vancouver Island, British Columbia, Canada , 2000 .

[14]  C. Scholz.  The Mechanics of Earthquakes and Faulting , 1990 .

[15]  P. Vincent,et al.  Present‐day vertical deformation of the Cascadia Margin, Pacific Northwest, United States , 1994 .

[16]  M. Murray,et al.  Strain accumulation along the Cascadia Subduction Zone , 2000 .

[17]  John J. Clague,et al.  Postglacial rebound at the northern Cascadia subduction zone , 2000 .

[18]  L. Simarski.  EOS scrutinized again , 1991 .

[19]  Ray J. Weldon,et al.  Tectonic role of active faulting in central Oregon , 1993 .

[20]  Herb Dragert,et al.  GPS deformation in a region of high crustal seismicity: N. Cascadia forearc , 2002 .

[21]  J. Clague,et al.  O-975 Estimates of Coastal Subsidence from Great Earthquakes in the Cascadia Subduction Zone , 2002 .

[22]  J. Clague,et al.  Foraminiferal evidence for the amount of coseismic subsidence during a late holocene earthquake on Vancouver Island, West Coast of Canada , 1996 .

[23]  Kenji Satake,et al.  Time and size of a giant earthquake in Cascadia inferred from Japanese tsunami records of January 1700 , 1996, Nature.

[24]  Kelin Wang,et al.  Thermal constraints on the seismogenic portion of the southwestern Japan subduction thrust , 1995 .

[25]  Kelin Wang,et al.  Three-dimensional viscoelastic interseismic deformation model for the Cascadia subduction zone , 2001 .

[26]  T. Sagiya,et al.  Coseismic slip resolution along a plate boundary megathrust: The Nankai Trough, southwest Japan , 1999 .

[27]  B. F. Atwater,et al.  Evidence for Great Holocene Earthquakes Along the Outer Coast of Washington State , 1987, Science.

[28]  Herb Dragert,et al.  GPS‐determination of along‐strike variation in Cascadia margin kinematics: Implications for relative plate motion, subduction zone coupling, and permanent deformation , 2001 .

[29]  Hiromichi Tsuji,et al.  Silent fault slip following an interplate thrust earthquake at the Japan Trench , 1997, Nature.

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

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

[32]  Kelin Wang,et al.  The rupture zone of Cascadia great earthquakes from current deformation and the thermal regime , 1995 .

[33]  R. Simpson,et al.  Northward migration of the Cascadia forearc in the northwestern U.S. and implications for subduction deformation , 2001 .

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

[35]  P. Friele,et al.  Holocene sea-level change on the central west coast of Vancouver Island, British Columbia , 1993 .

[36]  W. Peltier,et al.  ICE-3G: A new global model of late Pleistocene deglaciation based upon geophysical predictions of po , 1991 .

[37]  Douglas S. Wilson.  Confidence intervals for motion and deformation of the Juan de Fuca Plate , 1993 .

[38]  Brian F. Atwater,et al.  Recurrence Intervals for Great Earthquakes of the Past 3,500 Years at Northeastern Willapa Bay, Washington , 1997 .

[39]  John J. Clague,et al.  Evidence for large earthquakes at the Cascadia Subduction Zone , 1997 .

[40]  Kelin Wang.  Stress–strain ‘paradox’, plate coupling, and forearc seismicity at the Cascadia and Nankai subduction zones , 2000 .

[41]  R. Blakely,et al.  Fore-arc migration in Cascadia and its neotectonic significance , 1998 .

[42]  R. Riddihough.  Recent movements of the Juan de Fuca Plate System , 1984 .

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

[44]  G. Rogers.  Seismotectonics of British Columbia , 1983 .

[45]  Kelin Wang,et al.  Three‐dimensional dislocation model for great earthquakes of the Cascadia Subduction Zone , 1997 .

[46]  W. Peltier,et al.  Ice Age Paleotopography , 1994, Science.

[47]  C. Goldfinger,et al.  Rotation and plate locking at the Southern Cascadia Subduction Zone , 2000 .

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

[49]  K. Walker,et al.  TIDAL MARSH STRATIGRAPHY, SEA-LEVEL CHANGE AND LARGE EARTHQUAKES—II: SUBMERGENCE EVENTS DURING THE LAST 3500 YEARS AT NETARTS BAY, OREGON, USA , 1998 .

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

[51]  R. Simpson,et al.  Post 12 m.y. rotation of southwest Washington , 1982 .

[52]  H. Dragert,et al.  Crustal Deformation Measurements on Vancouver Island, British Columbia: 1976 to 1988 , 1990 .

[53]  R. Yeats,et al.  Tectonics of the Neogene Cascadia forearc basin: Investigations of a deformed late Miocene unconformity , 2000 .