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OUTLINE OUTLINE � EM and Earthquake Prediction � EM and Earthquake Prediction - The Red Flag Problems - The Red Flag Problems � Solutions: Use Earthquakes to relate EM � Solutions: Use Earthquakes to relate EM to the fault failure process to the fault failure process � Conclusions � Conclusions
EM and Earthquake Prediction EM and Earthquake Prediction - The Red Flag Problems - The Red Flag Problems After Fraser-Smith et al. 1990) � Predictions with data shown � Predictions with data shown for just a short time before a for just a short time before a single event. As is obvious, it single event. As is obvious, it is always possible to find is always possible to find some change in any some change in any parameter before any point in parameter before any point in time. Believability comes from time. Believability comes from demonstration of relation to demonstration of relation to mechanics and repeatability. mechanics and repeatability.
EM and Earthquake Prediction EM and Earthquake Prediction - The Red Flag Problems - The Red Flag Problems Sept, 20, 1999 � Predictions using data from a � Predictions using data from a single station not necessarily single station not necessarily close to an eq. with big close to an eq. with big change before the eq. but no change before the eq. but no Stock Market Averages changes observed during the changes observed during the eq. when major deformation, eq. when major deformation, stress change, seismicity, etc stress change, seismicity, etc occur. occur.
EM and Earthquake Prediction EM and Earthquake Prediction - The Red Flag Problems - The Red Flag Problems � Predictions with no tie to � Predictions with no tie to earthquake mechanics earthquake mechanics or available copious or available copious information on crustal information on crustal deformation, seismicity deformation, seismicity and conductivity data and conductivity data -extremely important -extremely important � Predictions without � Predictions without statistics showing statistics showing significance significance
Solution: Use Earthquakes to Solution: Use Earthquakes to relate EM to Fault Failure relate EM to Fault Failure � Coseismic Stress/Strain offsets � Coseismic Stress/Strain offsets � Dynamic Stress Waves � Dynamic Stress Waves (seismograms) (seismograms) � Traveling Ionospheric � Traveling Ionospheric Disturbances (TIDS) Disturbances (TIDS)
Coseismic Stress/Strain offsets Coseismic Stress/Strain offsets – Parkfield M6, Sept 28, 2004 – Parkfield M6, Sept 28, 2004
Comparison with Seismic and Comparison with Seismic and Geodetic Models Geodetic Models -General Agreement -Overall, models quite tightly constrained -Fault Failure process thus generally well understood See BSSA, V96, S206-220, 2006
Piezomagnetic Models Piezomagnetic Models Simple uniform slip Inversion of geodetic data Inversion of geod./seismic data See BSSA, V96, S206-220, 2006
Dynamic Stress Waves Dynamic Stress Waves EM Seismogram for EM Seismogram for M6 2004 Parkfield M6 2004 Parkfield earthquake earthquake Expect EM effects from Expect EM effects from � � Stress wave Stress wave � � Ground shaking/rotation of EM instrument Ground shaking/rotation of EM instrument � � in Earths’ magnetic field - should be in Earths’ magnetic field - should be minimal but depends on installation. minimal but depends on installation. Signals observed starting with first P Signals observed starting with first P � � arrival with larger signals during S wave arrival with larger signals during S wave arrivals arrivals
Comparison between Comparison between EM and Strain EM and Strain Some correspondence for P Some correspondence for P � � waves (EW mag, NS elec) waves (EW mag, NS elec) and some correspondence for and some correspondence for S waves (vertical mag, NS S waves (vertical mag, NS mag, EW mag) mag, EW mag) Thus, stress related effects Thus, stress related effects � � provide some contributions to provide some contributions to EM data but not the entire EM data but not the entire story. story.
Quasi-static Piezomagnetic Quasi-static Piezomagnetic Dynamic Stress Model Dynamic Stress Model Assume uniform magnetization and Assume uniform magnetization and � � stress sensitivity of 2 A/m and 3E-3/bar stress sensitivity of 2 A/m and 3E-3/bar and 0.01 S/m and 3E-4/bar for and 0.01 S/m and 3E-4/bar for conductivity. conductivity. Assume E=5.3 GPa, Vp=5 km/sec, Assume E=5.3 GPa, Vp=5 km/sec, � � Vs=2.5 km/sec, Vr=2.3 km/sec in finite Vs=2.5 km/sec, Vr=2.3 km/sec in finite element grid element grid Assume uniform half space and uniform � Assume uniform half space and uniform � slip. slip. � Problems � Problems Computationally intensive. � Computationally intensive. � Spatial smoothing needed to get finite � Spatial smoothing needed to get finite � solutions for magnetic fields. solutions for magnetic fields.
Quasi-static Piezomagnetic Quasi-static Piezomagnetic Dynamic Stress Model Dynamic Stress Model � More complex slip model � More complex slip model needed from seismic needed from seismic inversion. inversion. � Correction needed for local � Correction needed for local ground response. Need to ground response. Need to determine surface Green’s determine surface Green’s functions from co-located functions from co-located surface seismometer. surface seismometer. � Model fits only the low � Model fits only the low frequency components in frequency components in the EM seismogram. the EM seismogram.
P Wave Data Comparison P Wave Data Comparison Synthetic Data Synthetic Data
Traveling Ionospheric Traveling Ionospheric Disturbances (TIDS) Disturbances (TIDS) � Generated by acoustic (gravity) � Generated by acoustic (gravity) waves caused by static and waves caused by static and dynamic ground displacement dynamic ground displacement with earthquakes and explosive with earthquakes and explosive eruptions from volcanoes that eruptions from volcanoes that are coupled into the atmosphere are coupled into the atmosphere and trapped in the Ionosphere and trapped in the Ionosphere Earth wave guide. Earth wave guide. � Various phases propagate at � Various phases propagate at 200-300 m/s (Francis, 1976) 200-300 m/s (Francis, 1976) (see Mueller and Johnston, 1987
Conclusions Conclusions Static stress field offsets, dynamic stress waves and acoustic waves from Static stress field offsets, dynamic stress waves and acoustic waves from � � earthquakes are the largest earthquake related stress changes in the earthquakes are the largest earthquake related stress changes in the Earth’s crust. Earth’s crust. EM changes from these phenomena can be used to relate electromagnetic EM changes from these phenomena can be used to relate electromagnetic � � signals to real crustal behavior consistent with geodetic and seismic signals to real crustal behavior consistent with geodetic and seismic observations. observations. Other EM signals related to other processes with earthquakes also occur Other EM signals related to other processes with earthquakes also occur � � and these provide important new information about the earthquake and these provide important new information about the earthquake process and local ground response. process and local ground response. It is apparent from our EM data together with data from multiple high- It is apparent from our EM data together with data from multiple high- � � resolution strain, seismic and geodetic instruments in the near-field of resolution strain, seismic and geodetic instruments in the near-field of earthquakes that precursory signals do NOT scale with earthquake size. earthquakes that precursory signals do NOT scale with earthquake size. These data argue for nucleation runaway models of earthquake failure and These data argue for nucleation runaway models of earthquake failure and against concepts of large scale earthquake preparations zones. against concepts of large scale earthquake preparations zones.
Coseismic Stress/Strain offsets Coseismic Stress/Strain offsets - North Palm Strings, Landers - North Palm Strings, Landers
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