Viscoelastic Flow in the Lower Crust After the 1992 Landers, California, Earthquake

• Published in: Science (American Association for the Advancement of Science) Vol. 282; no. 5394; pp. 1689 - 1692
• Main Authors: Deng, Jishu, Gurnis, Michael, Kanamori, Hiroo, Hauksson, Egill
• Format: Journal Article
• Language: English
• Published: Washington, DC American Society for the Advancement of Science 27-11-1998; American Association for the Advancement of Science; The American Association for the Advancement of Science
• Subjects: Artificial satellites; Deformation; Earth sciences; Earth, ocean, space; Earthquakes; Earthquakes, seismology; Environmental aspects; Exact sciences and technology; Geodetic research; Geology; Global positioning systems; Internal geophysics; Modeling; Mohorovicic discontinuity; Natural disasters; Navigation satellites; Observations; Plate tectonics; Profiles; Seismological research; Seismology; Solid-earth geophysics, tectonophysics, gravimetry; Strikes; Three dimensional modeling; Viscoelasticity; Viscosity; Basin and Range Province; United States; California; United States > US; Landers California; rheology; shear; satellite methods; lower crust; earthquakes; North America; continental crust; right-lateral faults; rupture; Global Positioning System; strike-slip faults; viscosity; extension tectonics; positioning; displacements; three-dimensional models; viscoelasticity; fault displacements; deformation; geodesy; seismic risk
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.282.5394.1689

Space geodesy showed that broad-scale postseismic deformation occurred after the 1992 Landers earthquake. Three-dimensional modeling shows that afterslip can only explain one horizontal component of the postseismic deformation, whereas viscoelastic flow can explain the horizontal and near-vertical displacements. The viscosity of a weak, about 10-km-thick layer, in the lower crust beneath the rupture zone that controls the rebound is about 10$^{18}$ pascal seconds. The viscoelastic behavior of the lower crust may help to explain the extensional structures observed in the Basin and Range province and it may be used for the analysis of earthquake hazard.