Seismogeodesy for rapid earthquake and tsunami characterization

Transcription

1 Seismogeodesy for rapid earthquake and tsunami characterization Yehuda Bock Scripps Orbit and Permanent Array Center Scripps Institution of Oceanography READI & NOAA-NASA Tsunami Early Warning Projects IN32A: Near Real-Time Data for Earth Science and Space Weather Applications 2016 Fall AGU Meeting, San Francisco December 14, 2016

2 Local tsunami warning system Current tsunami warning systems based on seismic data may significantly underestimate the magnitude of a tsunamigenic earthquake in the critical first few minutes of an event leading to inaccurate forecasts for those in the epicentral region

3 Global & Regional Continuous GNSS Stations Cascadia Subduction Zone Mw 9.0 earthquake & tsunami similar to 2011 Great Japan Earthquake

4 Seismogeodesy: Optimal Integration of GNSS and Seismic Data Seismic Geodetic Seismogeodetic Hz Doubly Integrate Accelerations P-wave? yes 1-10 Hz Precise Point Positioning (PPP) P-wave? no less precise Hz 1-10 Hz PPP-ARA/ Kalman Filter P-wave? yes Advantages of Seismogeodesy Provides very high-rate displacement and velocity waveforms Provides broadband instrument that does not clip even in the near field of the largest earthquake Reduces effects of baseline offsets in doubly-integrated accelerometer data and preserves static offset Not affected by magnitude saturation for earthquakes greater than ~M7.5 Like seismic data, able to detect P-wave arrivals, not possible with GNSS data alone Very well suited for accurate earthquake early warning for local >Mw4-5 earthquakes, and rapid magnitude and fault mechanism for local tsunami warning

5 Seismogeodetic waveforms for two earthquakes 2011 Mw9.0 Tohoku-oki, Japan Verified seismogeodetic method for earthquakes in California, Japan, Nepal and Chile 2010 Mw7.2 El Mayor-Cucapah, Mexico Broadband seismometer with no clipping in the near-source region of any magnitude earthquake Melgar et al., GRL, 2013 Bock et al., BSSA, 2011

6 Real-Time GNSS Stations Real-Time Seismogeodetic Stations

7 Real-Time Seismogeodetic Station Mt. Soledad, La Jolla Radio Antennas Antenna/Radome Solar Panel MEMS Met Sensors SIO MEMS Accelerometer Monument Equipment Enclosures: GNSS, Geodetic Module, Batteries, Radio Photo Courtesy D. Glen Offield

8 Local tsunami early warning simulation for Cascadia Mw8.5 earthquake using current West Coast GNSS stations Earthquake Simulation Seafloor Deformation Tsunami Simulation Tsunami Amplitude (m) Vertical Deformation (m) Figure from Diego Melgar UC Berkeley Slide and movie prepared by Jessie Saunders

9 Elements of Seismogeodetic Early Warning Elements of Local Tsunami Warnings Detection & Location Rapid magnitude estimation Rapid earthquake fault mechanism Issue warning Refinement Fault slip model Seafloor motion model Tsunami model Prediction of runup & inundation Issue refined warning

10 NOAA-NASA Tsunami Warning Project NOAA National & Pacific Tsunami Warning Centers, Central Wash. U., Jet Propulsion Lab, Scripps Inst. Oceanography, UC Berkeley, Univ. Washington

11 GWORM system: Data Entry GPS displacements in geojson format merged from three independent analysis centers: CWU, JPL and SIO with fail-over from each center Seismogeodetic displacements and velocities in tracebuf2 format from SIO PPP-ARA (Geng et al.)

12 GWORM system: Earthquake Detection & Location GWORM system: Modeling

13 Seismogeodetic Earthquake Picking 2016 Mw5.2 Borrego Springs Earthquake Pick_sg STA/LTA algorithm to detect P-waves from 100 Hz accelerometer or seismogeodetic velocity data. Algorithm is implemented at individual stations, thus thresholds can be adjusted to reflect noise characteristics of the station. Detections at each station are corroborated by additional stations. Once 4 stations indicate a detection, the subsequent seismogeodetic modules are triggered. Prepared by Dara Goldberg

14 Hypo_sg Earthquake Early Warning: 2016 Mw5.2 Borrego Springs Earthquake Prepared by Dara Goldberg

15 Earthquake Magnitude Scaling Modules Mw_Pd Mw_PGD Figure from Crowell et al. (2013) P d scaling horizontal components, seismogeodetic PGD scaling, all components, GNSS only Figure from Melgar et al. (2015) Modified by Jessie Saunders P-wave displacement amplitude (P d ) Peak Ground Displacement (PGD) GNSS only sensitivity ~ 15 mm Seismogeodetic SIO GAP sensitivity ~ 8 mm These methods require accurate, high-rate displacement data, which are difficult to obtain in the near-field in real time using traditional seismic instruments that suffer from magnitude saturation

16 Line source rapid centroid moment tensor solution: fastcmt fastcmt_sg 2010 Mw 7.2 El Mayor-Cucapah 2011 Mw 9.0 Tohoku-oki Lat = Lon = Depth = 4 km Lat = Lon = Depth = 48 km Moment Tensor (Scale 1x10^19 Nm) Mrr = Mtt = Mpp = Moment Tensor (Scale 1x10^21 Nm) Mrr = Mtt = Mpp = Mrt = Mrp = Mtp = Mrt = Mrp = Mtp = Best Double Couple Plane Strike Dip Rake NP Best Double Couple Plane Strike Dip Rake NP NP NP Updated until shaking is complete and final coseismic offset is determined. fastcmt produces accurate focal mechanisms within 2-3 minutes of earthquake onset. It provides information about faulting mechanism, and is indicative of the likelihood that an event could be tsunamigenic. Prepared by Dara Goldberg

17 Finite Fault Slip Model Modules FaultSlip_sg Total slip model for the Mw9.0 Tohoku-oki earthquake. Dashed lines are depth contours of the subducting slab in km. Static model available within about 3 minutes Static model available once wave gauge data are ingested Melgar and Bock, JGR, 2015 (a) Model from land-based seismogeodetic data only (b) Estimate sea floor deformation (c) Model from seismogeodetic and wave gauge data (GNSS buoys and ocean-bottom pressure sensors)

18 Seismogeodetic System: Land & Ocean Earthquake models Seafloor deformation Tsunami propagation Melgar & Bock, JGR, 2013,2015

19 Tsunami Model for the 2011 Mw9.0 Tohoku-oki Earthquake Tsunami_sg Accurate but time consuming. Simpler system published by Melgar et al. in GRL suitable for real-time operations. Sendai Bay Fukushima Sendai Bay 10km 100km Blue dots on shore denote tsunami inundation measured by post-event land surveys showing good agreement between the model and land surveys (Melgar and Bock, JGR, 2015)

20 Seismogeodesy for rapid earthquake and tsunami characterization Thank You! Questions? IN32A: Near Real-Time Data for Earth Science and Space Weather Applications 2016 Fall AGU Meeting December 14, 2016