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Imaging seismic waves from space Rémi Michel 1,2, Sébastien Leprince 1, Serge Primet 3, S. Somala 1, Jean-Paul Ampuero 1, Nadia Lapusta 1, Jean-Philippe Avouac 1 1 California Institute of Technology, Pasadena, USA 2 Commissariat a l’Energie Atomique, Saclay, France 3 Institut d’Optique, Palaiseau, France

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Motivation Source Model of the 1999, Mw 7.1 Duzce Earthquake. Data: SPOT offsets, inSAR, GPS, Seismograms (Konca et al, BSSA, 2010)

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Motivation Source Model of the 1999, Mw 7.1 Duzce Earthquake: An initial crack-like rupture which evolve into a super-shear pulse (Konca et al, BSSA, 2010)

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Simulation of a seismic rupture: horizontal strike-parallel component of the velocity field), computed for a theoretical Mw 7.0 earthquake simulated using a rate&state friction law and the Spectral Element Method (e.g., Kaneko, Lapusta and Ampuero, 2009) Motivation 50km t=15s

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The determination of a kinematic source model from the inversion of static ground displacement and seismograms measured at a sparse set of seismic stations is an ill-posed problem. …but such models are needed to investigate Earthquake physics. Motivation

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RequirementsComments Field of view# 550X250 kmMain Shocks, California SamplingSpatial# 100 mOk for Mw > 5.5 Poor for Mw < 5.5 ? Temporal# 1 Hz Accuracy# 1cm.s -1 Similar to accelerometers Requirements -0.10.1S -1 Mw7Mw7 Mw6Mw6 50km

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Airborne/Space Systems InstrumentComments Drones Field Of View Airplanes FOV, temporal sampling ? Balloons Stability, FOV Earth Orbiter Low, Medium Temporal Sampling FOV # 1000km : Huge Constellations Geostationary Instrumentation? {Radar GESS Geosynch Radar Study } Optics Passive Imagery Limited to Clear Sky, Daylight ? A Large Geostationary Optical Telescope?

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Photometry Essentials L:radiance, : reflectance, S : atmosphere spherical reflectance Movie [0.4-2.5 m] Wavelength ( m) Sun RadianceAtmosphere Transmittance Wavelength ( m) Ground Reflectance Wavelength ( m) Atmospheric Turbulence

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SignalsTechniqueGeostationary Issues Horizontal Deformation Optical flow, Correlation Telescope size (Resolution) Detection Data flow 1/100 pixel Slope (Radiance) VariationPhotoclinometry Telescope size (Photometry) I/I=2.10 -5 Detection Stability Topographic LiDAR Differential topography Laser Energy! #100 photons=5cm Doppler Shift (atmosphere) Rayleigh=>Acoustic Wind Velocimeters Small Doppler 10 cm.s -1 Complex Signal Measurable quantities with Optical Systems

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Sun Poisson Incidence Atmosphere Steering (geometry) Kolmogorov Shift < few centimeters<6cm Blur < few centimeters<6cm Dancing (geometry) Scintillation (photometry) Rytov Ground Bidirectional Reflectance Distribution Function Natural, 1-100m Urban TBD (high level), lights, damages, etc. Vegetation TBD Shakened ground TBD Natural Light Fluctuations [10Hz-1Hz]

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Horizontal offsets Measured by Correlation or Optical Flow 1/100 of the pixel size. SNR 1000 (reflectance 0.15, back-illuminated CCD) : 0.03 s per frame for 4m. Stability is an issue for data management and not for accuracy.

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Photoclinometry Accuracy possible up to [10 -4 -10 -5 ] (number of detected photons [10 10 – 10 11 ]) =0.15, pixel size : 100m, integration time 0.03s, most unfavorable incidence angle # 11 degrees

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Simulations-Horizontal offsets Synthetic Telescope 4.0m Telescope 10.m Mw 7.1, t=15s Mw 6.0 t=4.22s Mw 6.0 t=4.22s Mw 6.0 t=4.22s Model (Mw 7.1, 30s, 2Hz, pixel:100m) and 2 critical telescope diameters (1Hz, pixel:100m)

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Telescope 10.0m -0.10.1S -1 Accuracy 1/50 th pixel Telescope 4.0m Simulations- Horizontal offsets

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Modele 7.0m 4.0m 10.0m

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Simulations-Photoclinometry Synthetic Simulation (4m) 0.004 rad.s -1 (Mw7)

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Conclusions Optics-Geostationary : a solution to measure seismic waves and other transients 40% of Earthquakes in Southern California, #1.2 per year with Mw 6 and above Telescope size is critical, large field of view (up to 4 degrees?) Less than 10% light budget, more applications possible Payload sub-critical Further investigations required Atmosphere, aliasing, moonlight, weather, wide field up to 4 degrees telescope design, geostationary environment, laser, etc. Will require new analysis technique in seismology. Conclusions

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4.0m Ariane V Compatible 7.0m Challenging 10.0m Challenging 4.0m 7.0m 10.0m Horizontal Velocities [-0.4,+1.9] (m.s-1) ModelA A’ A Transect Model of strike slip fault (Mw 7.1), Field of view 60*24km, 1Hz, ground resolution 100m Accuracy of Optical Correlation = f( telescope, geostationary)

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