I Studies In Crustal Deformation Using Gps And Tiltmeters

Earthquake and Volcano Deformation is the first textbook to present the mechanical models of earthquake and volcanic processes, emphasizing earth-surface deformations that can be compared with observations from Global Positioning System (GPS) receivers, Interferometric Radar (InSAR), and borehole strain- and tiltmeters. Paul Segall provides the physical and mathematical fundamentals for the models used to interpret deformation measurements near active faults and volcanic centers. Segall highlights analytical methods of continuum mechanics applied to problems of active crustal deformation. Topics include elastic dislocation theory in homogeneous and layered half-spaces, crack models of faults and planar intrusions, elastic fields due to pressurized spherical and ellipsoidal magma chambers, time-dependent deformation resulting from faulting in an elastic layer overlying a viscoelastic half-space and related earthquake cycle models, poroelastic effects due to faulting and magma chamber inflation in a fluid-saturated crust, and the effects of gravity on deformation. He also explains changes in the gravitational field due to faulting and magmatic intrusion, effects of irregular surface topography and earth curvature, and modern concepts in rate- and state-dependent fault friction. This textbook presents sample calculations and compares model predictions against field data from seismic and volcanic settings from around the world. Earthquake and Volcano Deformation requires working knowledge of stress and strain, and advanced calculus. It is appropriate for advanced undergraduates and graduate students in geophysics, geology, and engineering. Professors: A supplementary Instructor's Manual is available for this book. It is restricted to teachers using the text in courses. For information on how to obtain a copy, refer to: http://press.princeton.edu/class_use/solutions.html

This book takes an in depth look at a novel methodology for analyzing Global Positioning System (GPS) data to obtain the highest possible resolution surface imaging of tectonic deformation sources without prescribing the nature of either the sources or the subsurface medium. GPS methods are widely used to track the surface expression of crustal deformation at tectonic plate boundaries, and are typically expressed in terms of velocity fields or strain rate fields. Vertical derivatives of horizontal stress (VDoHS) rates at the Earth’s surface can also be derived from GPS velocities, and VDoHS rates provide much higher resolution information about subsurface deformation sources than velocities or strain rates. In particular, VDoHS rates allow for high precision estimates of fault dips, slip rates and locking depths, as well as objective characterization of previously unknown (or hidden) tectonic deformation zones.

Vancouver Island, located in southwestern coastal British Columbia, overlies the northern portion of the Cascadia Subduction Zone. This region is characterized by extensive seismicity which includes M ∼ 7 crustal earthquakes and less frequent M ∼ 9 megathrust events. Crustal deformation measurements have been carried out in this region since 1978 using various geodetic field techniques: levelling, tide gauge studies, precise gravity, laser ranging, and most recently, GPS. Earlier survey data provided key constraints to elastic slip-dislocation models for estimating the size and location of the rupture area for the next subduction-thrust earthquake. Recent estimates of crustal motions within the North Cascadia Margin based on both campaign GPS network surveys and up to 6.5 years of data from continuous GPS sites are consistent with the strain accumulation expected from a locked subduction fault. The deformation vectors are in the direction of plate convergence within the uncertainty of plate motion models. The observed strain rate across Vancouver Island is, however, smaller (by approximately a factor of 1.5) than the dislocation model prediction, suggesting the presence of visco-elastic effects. Crustal deformation measurements for central Vancouver Island fail to resolve motions that could be associated with the occurrence of large crustal earthquakes, and also suggest that the extent of the seismogenic subduction thrust zone north of the Nootka Fault Zone is extremely limited.