Properties of seismic fault zone waves and their utility for imaging low-velocity structures

摘要: A two-dimensional solution for the scalar wave equation in a model of two vertical layers between quarter spaces is used to study properties seismic waves laterally heterogeneous low-velocity structure. The waves, referred as fault zone include head internal reflections, and trapped waves. analysis aims clarify dependency on media velocities, attenuation coefficients, layer widths, source-receiver geometry. Additional calculations with extreme provide examples that may be relevant volcanic geothermal domains. interference patterns controlling change number reflections This increases propagation distance along structure, decreases width, (for given length scales) velocity contrast. relative lateral position source within modifies die scales associated influences resulting pattern. Low values Q affect considerably dominant period overall duration Thus there are significant tradeoffs contrast, location zone, Q. depth receiver coordinates determine particular point where pattern sampled observed motion strong function both coordinates. connecting sources generating observation points appreciable amplitude can over an order magnitude larger than width. Calculations cases P ∼200 m s−1, modeling dike or crack fluid gas, show conspicuous persisting oscillations. results resemble aspects data If these exist records, their explicit recognition will help separate structural effects aid interpretation volcano-seismology signals. Although parameters governing significant, each variable has its own signature, constrained by additional geophysical data. Simultaneous many waveforms appropriate resolve various high-resolution image.