Earthquake Early Warning in California: Evaluating Hardware and Software Margaret Hellweg, Richard Allen, Maren Böse, Holly Brown, Georgia Cua, Doug Given, Egill Hauksson, Tom Heaton, Tom Jordan, Oleg Khainovski, Phil Maechling, Doug Neuhauser, David Oppenheimer, Kalpesh Solanki, Michael Zeleznik University of California, Berkeley California Institute of Technology ETH Zurich USGS Pasadena Southern California Earthquake Center USGS Menlo Park Saya Systems Funded by CISN California Integrated Seismic Network

What is earthquake early warning? Seismic Stations P-wave fault S-wave

What is earthquake early warning? minimal telemetry delays but less robust warning time is the S-P time best chance of warning at epicenter Single station approach 1st Station to detect P-wave arrival Issue warning? Seismic Stations P-wave fault S-wave CISN California Integrated Seismic Network EEW  “On-site” method

What is earthquake early warning? Multiple stations detect P-wave arrival Seismic Stations P-wave fault S-wave

What is earthquake early warning? Multiple stations detect P-wave arrival Estimate the extent of rupture Seismic Stations P-wave fault S-wave Rupture

What is earthquake early warning? Network based approach Multiple stations detect P-wave arrival Estimate the extent of rupture Issue warning longer delay but more robust difficult to warn at epicenter transmit warning ahead of shaking …greater warning times Seismic Stations P-wave fault CISN California Integrated Seismic Network EEW S-wave  “ElarmS” and “Virtual Seismologist” methods Rupture Shaking

What is earthquake early warning? More stations detect P-wave arrival Estimate the extent of rupture Issue warning More information  update warning Seismic Stations P-wave fault S-wave Rupture Shaking

California Integrated Seismic Network August 2006 – July 2009 statewide testing CISN California Integrated Seismic Network EEW Goal: evaluate real-time performance of early warning algorithms Aug ‘06 Year 1: Initial real-time outputs from EEW algorithms Year 2: Statewide processing; Add uncertainty estimates; website display Year 3: Evaluation of past and future performance Year 1: Initial real-time outputs from EEW algorithms Year 2: Statewide processing; Add uncertainty estimates; website display Year 3: Evaluation of past and future performance Currently at 28 mths Jul ‘09  specifications for implemented early warning system equipment requirements (stations) telemetry processing …the next generation of geophysical networks 8

California Integrated Seismic Network August 2006 – July 2009 State-wide testing CISN California Integrated Seismic Network EEW Goal: evaluate real-time performance of early warning methods Distributed waveform processing Each algorithms runs at one datacenter Reporting to SCEC Three algorithms: Archive/website SCEC/USC 1. Onsite warning (S11A-1727) Caltech/U. Taiwan 2. Virtual Seismologist (S11A-1724, S14B-06) Caltech/ETH 3. ElarmS (S11A-1726 , S11A-1725) UC Berkeley Algorithm Evaluation: UC Berkeley USGS Menlo Park Alert information and summaries (S11A-1728) SCEC/USC Caltech/USGS Pasadena

τc-Pd On-site Warning Algorithm (S11A-1727) CISN California Integrated Seismic Network EEW τc-Pd On-site Warning Algorithm (S11A-1727) 2007-2008: 58 earthquakes with 3.0 ≤ Mw ≤ 5.4 Mw5.4 Chino Hills 07/29/2008: 60 triggers Uncertainties after station corrections: Mw: ±0.5; log(PGV): ±0.3; MMI: ±0.7 HH estimated Mw=4.4…6.5 (median: 5.6) First estimate: Mw=5.6 (CI.PSR, 10 sec after O.T.) → 6 sec warning time at LA City Hall Magnitude Peak Ground Velocity Warning delays ~ 9-16 sec 10

Virtual seismologist (S11A-1724, S14B-06) CISN California Integrated Seismic Network EEW Virtual seismologist (S11A-1724, S14B-06) Regional network approach Bayesian approach: Include likelihood of earthquake given past observations e.g. Gutenberg-Richter relation and distribution of previous seismicity Triggers on P-waves Uses envelope functions of waveforms Magnitude derived from 3 sec of the P-wave Predicts the distribution of ground shaking Finite fault discriminate Cua & Heaton 2007 Real-time in SC since 13 July 2008 Initial estimate within 10-30 s of origin time Mw: ±1 for 97% of events Fig captions are included (cropped off display) Left: Figure 5.11 from Yamada’s thesis: probability that a station is near source based on their discriminat function Right: Figs 6.5 and 6.7 from Yamada’s thesis: back projection of station displacement onto the fault; backprojected slip estimates and the estimated slip from kinematic inversions Next steps: Statewide processing Site conditions EQ/noise discrimination Yamada & Heaton in review

California Integrated Seismic Network CISN California Integrated Seismic Network EEW ElarmS-RT (S11A-1726 , S11A-1725) Statewide (Nov 08) (waveform processing at UCB, USGS-MP and Caltech) Regional network approach Triggers on P-waves, uses arrival times, frequency and amplitude of P-wave. Uses PGA and PGV as they become available. Predicts the distribution of ground shaking using ShakeMap approach  AlertMaps AlertMaps – ElarmS-RT – MW5.4 October 30, 2007 trigger time + 1 sec + 2 sec + 3 sec

Testing Algorithm Performance (S11A-1728) CISN California Integrated Seismic Network EEW Testing Algorithm Performance (S11A-1728) Performance summaries (Location/Magnitude currently implemented) generated every night (2mo,4mo,6mo and cumulative time periods). Generating Summaries for ElarmS (UCB), TauC (Caltech),and Virtual Seismologist ( ETH) CISN EEW Testing site available at: http://www.scec.org/eew Login: guest Pwd: cisneew Magnitude Accuracy Warning Delay with current CISN network Theoretical Warning Delay with no telemetry or processing delays 13

California Integrated Seismic Network CISN California Integrated Seismic Network EEW Perspectives …