HR: 1340h
AN: S23A-0282    [Abstracts]
TI: GEMS: the Opportunity for Stress-Forecasting all Damaging Earthquakes Worldwide
AU: * Crampin, S
EM: scrampin@ed.ac.uk
AF: School of GeoSciences Edinburgh University, Grant Inst. West Mains Road, Edinburgh, EH9 3JW United Kingdom
AB: Worldwide observations of shear-wave splitting indicate that rocks in the crust are pervaded by stress-aligned fluid-saturated grain-boundary cracks. These cracks are so closely spaced that they verge on fracture-criticality and failure in earthquakes. The evolution of such cracked rocks before fracture-criticality is reached can be modeled by anisotropic-poro-elasticity (APE). APE-modeling matches a huge range of phenomena pertaining to cracks, stress, and shear-wave splitting. This has allowed the accumulation of stress to be monitored, with hindsight, before about 12 earthquakes worldwide with magnitudes ranging from ML1.7 to Ms7.7, using swarms of small earthquake as shear-wave source. The time and magnitude of one M5 earthquake was successfully stress-forecast. Shear-waves carry no information about location, but precursory data predicted the fault-break. Suitably-persistent swarms of earthquakes are rare, and routine stress-forecasting requires controlled-source measurements in crosshole observations between adjacent boreholes in stress-monitoring-sites (SMSs). The first preliminary SMS in Iceland, using the highly-repeatable Downhole Orbital-Vibrator (DOV) source, recorded spectacularly sensitive anomalies in: crosswell Vp, Vs1, Vs2, and Vs2-Vs1 (anisotropy); there were also well-level changes; and changes in NS and EW GPS measurements, all correlating with low-level seismicity (energy equivalent to one M$\sim$3.5 earthquake) at 70km-distance. These confirm the science and technology of SMSs for monitoring stress accumulation before earthquakes. The sensitivity means that SMS networks on 400km-grids, say, would be able to recognize the accumulation of stress before all earthquakes M$>$5 within the network. Consequently, GEMS, a global network of SMSs on a 400km grid, would: 1) stress-forecast the times and magnitudes of all damaging earthquakes (M greater or equal to 5, say) worldwide; 2) provide data for stress-forecasting service analogous to weather-forecasting; 3) provide control for reducing the potential for large earthquakes threatening vulnerable locations by monitoring the effects of massive hydraulic operations nearby; 4) provide a powerful new tool for investigating the evolution of the interior of the Earth and provide an intellectual stimulus for understanding the Earth in the 21st century.
UR: http://www.glg.ed.ac.uk/$\sim$scrampin/opinion/
DE: 7260 Theory and modeling
DE: 7294 Instruments and techniques
DE: 8164 Stresses--crust and lithosphere
DE: 7203 Body wave propagation
DE: 3902 Creep and deformation
SC: Seismology [S]
MN: 2004 AGU Fall Meeting