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Overview

The seismology application employs network technology to understand the physics of the seismic source and wave propagation effects.  Our long term goal is to understand and possibly predict earthquakes and their effects in terms of ground shaking at the surface and damage to buildings.  If prediction is ever to become a reality, we must improve our understanding of the physics of earthquakes. Specifically we seek to know both what starts and what stops an earthquake? Why does a magnitude 6.7 such as the 1994 Northridge earthquake not develop into a magnitude 9.4 as in the case of the 2004 Sumatra-Andaman earthquake? Why did the 1985 Michoacan earthquake topple high rise buildings in Mexico City 300 km away?

Our work combines understanding the driving tectonics that generates earthquakes (and volcanoes), the earthquake source itself, how geologic structure traps and focuses waves, and the effects of waves on buildings.  It is presently hampered by the paucity of seismic stations in critical areas, both above the earthquake and in the structures themselves, so that measurements are aliased.

Seismologists rely on coherence between waveforms so that correlated pulses in a seismogram may be mapped back into the Earth to understand their origin.  Because both the earthquake source and geological heterogeneities are fractal in nature, seismic pulses become incoherent after a spatial dimension of about a wavelength. Important earthquake-generated waves have wavelengths that range from tens of meters to tens of km.  At the small scale, simple geophone seismometers are adequate, while at the large scale elaborate broadband seismometers with active feedback are needed.