SCEC: An NSF + USGS Research Center

Evaluation of Earthquake Early Warnings as External Earthquake Forecasts

Philip MaechlingInformation Technology ArchitectSouthern California Earthquake Center (SCEC)7 May 2013

Premise: EEW In California Is Imminent

EEW Systems may forecast both event-specific and site-specific earthquake parameters

– Event Parameters• Magnitude

• Location

– Site-specific Parameters:• Site specific ground motion intensity

3

Earthquake Parameters Forecast by EEW Systems

Warning time depends on your location’s distance from where the earthquake begins. The slanted red line shows how warning time increases with distance from the epicenter. In this case, warning time increases beyond the 21 mile-radius blind zone with, for instance, approximately 10 seconds warning at 40 miles distance.

USER Module- Single site warning- Map view

CISN EEW Testing Center Test users

• predicted and observed ground motions

• available warning time• probability of false alarm•…

Decision Module(Bayesian)

CISN ShakeCISN Shake AlertAlertτc-Pd

On-site Algorithm

Virtual Seismologist

(VS)ElarmS

Single sensor Sensor network Sensor network

ShakeAlert Forecast Evaluation Problems:– Scientific publications provide insufficient information for independent

evaluation

– Data to evaluate forecast experiments are often improperly specified

– Active researchers are constantly tweaking their codes and procedures, which become moving targets

– Difficult to find resources to conduct and evaluate long term forecasts

– Standards are lacking for testing forecasts against reference observations

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Problems in Assessing Forecasts

Different algorithms produce different forecast parameters

• Some (e.g. On-site) produce site-specific information (PGA), event magnitude, but no origin time or distance to event

• Some (e.g. Vs) produces full event parametric information.• Some (e.g. Elarms) produce site specific ground motion estimates on a regular grid.• Some produce single values (On-site)• Some produce time-series with updates (Vs,Elarms)

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EEW Algorithm Differences

Applying the CSEP Testing Approach to Earthquake Early Warning Forecasts

CISN and SCEC received funding from USGS to develop and evaluate prototype network-based EEW:

SCEC has implemented the CISN Testing Center (CTC) to evaluate the system and seismological performance of the CISN and USGS ShakeAlert earthquake early warning prototype system.

Forecast Testing Should Increase Along with Forecast Impact

Public and Governmental Forecasts

Engineering and Interdisciplinary

Research

Collaborative Research Project

Individual Research Project

Computational codes, structural models, and simulation results versioned with associated tests.

Development of new computational, data, and physical models.

Automated retrospective testing of forecast models using community defined validation problems.

Automated prospective testing of forecast models over time within collaborative forecast testing center.

SCEC Computational Forecast Users

Scientific and Engineering Requirements for Forecast Modeling Systems

CISN Testing Center Design Goals and Constraints:

– Establish scientific framework for ShakeAlert Testing– Simple and inexpensive to develop and operate– Provide value to USGS and ShakeAlert developers– Communicate value of EEW testing to SCEC community and

CISN

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Scale of SCEC CTC Activity

Many CSEP testing principles are applicable to CISN EEW Testing. The following definitions need to be made to evaluate forecasts:– Exact definition of testing area– Exact definition of a forecast– Exact definition of input data used in forecasts– Exact definition of reference observation data– Measures of success for forecasts

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Design of an Experiment

Testing Center System Requirements

The goals of both an EEW and Earthquake Forecast Testing Center Goals (as outlined by Schorlemmer and Gerstenberger (2007)) describe what is needed to build trust in results:

Controlled EnvironmentTransparencyComparabilityReproducibility

Earthquake Catalog

Retrieve Data

FilterCatalog

Filtered Earthquake

Catalog

CISN EEW Performance Summary Processing

CISN EEW Testing Center and Web Site

ANSS Earthquake

Catalog

UCB/ElarmSNIEEW Data Source

CIT/OnSite EEW Data Source

Load Reports

EEW Trigger

Reports

EEW Trigger

Reports

Observed ANSS Data

CISN EEW Trigger Data

Produce Web

Summaries

CISN Testing Document

Decide if the 3 CSEP regions valid for EEW

• Region Under Test• Catalog Event Region• Buffer to avoid catalog issues

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Selection of a Testing Region

CISN Testing Document

CISN Testing Document

ShakeAlert Performance Testing System Overview

CISN Testing Center (top right) retrieves a daily earthquake catalog from ANSS Data Center (bottom right) and ShakeAlert performance logs from U.C. Berkeley (left). It then matches new ANSS events to Algorithm Alerts and Decision Module Alerts and plots (1) Event Performance summaries, and (2) Cumulative Performance Summaries

at USC

Types of ShakeAlert Performance Summaries Currently Available

Summaries posted online at: http://scec.usc.edu/scecpedia/CTC_Results

Cumulative ShakeAlert Performance Results for all ANSS catalog events M3.5+ with Network

Codes CI and NC between 4 March 2012 and 31 March 2013.

M4.5 at 2.4 km (1.5 mi) NE of The Geysers, CA 38.8123, -122.786, 2km Mar 14 2013 09:09:23 UTC 71954065

4.0 at 21.3 km (13.3 mi) SE of Markleeville, CA 38.5598, -119.616, 7km Jan 24 2013 23:25:51 UTC 71928201

EEW Science Testing introduces elements that CSEP has not had to consider– More difficult to determine information used in forecast.

– Especially difficult to determine information used when Bayesian approach is fully implemented

– Testing considered prospective if logged in real-time, not evaluated before earthquake occurs

– Warning-time of forecast (forecast term e.g. 60 second …1 second) varies by event

– Greater interest in summary of performance on an event by event basis. Should support push-based distribution of results after significant events.

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Conclusions

1. Broad impact of seismological technologies like EEW are great enough to warrant significant effort for evaluation.

2. Independent evaluation for EEW provides valuable service to agencies including CISN, USGS, CPEC, NEPC, and others.

3. Prospective must be done to before techniques will be accepted. 4. Similarities between problems lead to similar scientific techniques.5. Similarities between problems lead to similar technology approach and

potentially common infrastructure.6. “Neutral” third party testing has significant benefits to the science grous

involved in forecasting.7. CSEP infrastructure can be adapted for use in CISN EEW Testing

Centers.

End

Useful Information to Help Interpretation of CTC Performance Summary Results

• CTC performance summaries are focused on ShakeAlert speed of operation and earthquake event parameter forecasts. No site specific ground motion performance summaries have been developed.

• CTC ShakeAlert performance summaries compare ANSS event parameters to ShakeAlert alert event parameter forecasts. No searching for “false alerts” is currently done.

• Because ANSS Catalog is considered the correct observation, the CTC waits 48 hours after events to let the ANSS catalog settle down before generating CTC performance summaries.

• Cumulative summaries depend on the catalog filter criteria (date range, magnitude, and region) used to select ANSS catalog events. Currently, ANSS events are selected for Mag >= 3.5, Network ID NC or CI. And, we currently run for two time frames Sept 2011 through present and March 3, 2012 through present (considered the Elarms2 era).

• One pager event summaries are produced for new all ANSS events with Network ID NC or CI and Mag >= 3.0

EEW As An Earthquake Forecast

Earthquake Earthquake Warning systems predict final earthquake magnitude before it is known, possibly before earthquake rupture is completed.

-Most rigorous type of forecast testing in prospective testing.-We consider prospective EEW testing if the EEW algorithms log their forecasts in real-time, before final forecasts parameters (e.g. final magnitude) is known.