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The assumption of Poisson seismic-rate variability in CSEP/RELM experiments

A. M. Lombardi and W. Marzocchi
The assumption of Poisson seismic-rate variability in CSEP/RELM experiments
Bulletin of the Seismological Society of America (October 2010) 100 (5A): 2293-2300


Evaluating the performances of earthquake forecasting/prediction models is the main rationale behind some recent international efforts such as the Regional Earthquake Likelihood Model (RELM) and the Collaboratory for the Study of Earthquake Predictability (CSEP). Basically, the evaluation process consists of two steps: (1) to run simultaneously all codes to forecast future seismicity in well-defined testing regions; (2) to compare the forecasts through a suite of statistical tests. The tests are based on the likelihood score, and they check both the time and space performances. All these tests rely on some basic assumptions that have never been deeply discussed and analyzed. In particular, models are required to specify a rate in space-time-magnitude bins; it is assumed that these rates are independent and characterized by Poisson uncertainty. In this work we have explored in detail these assumptions and their impact on CSEP testing procedures when applied to a widely used class of models, that is, the Epidemic-Type Aftershock Sequence (ETAS) models. Our results show that, if an ETAS model is an accurate representation of seismicity, the same right model is rejected by the current CSEP testing procedures a number of times significantly higher than expected. We show that this deficiency is due to the fact that the ETAS models produce forecasts with a variability significantly higher than that of a Poisson process, invalidating one of the main assumptions that stands behind the CSEP/RELM evaluation process. Certainly, this shortcoming does not negate the paramount importance of the CSEP experiments as a whole, but it does call for a specific revision of the testing procedures to allow a better understanding of the results of such experiments.

ISSN: 0037-1106
EISSN: 1943-3573
Serial Title: Bulletin of the Seismological Society of America
Serial Volume: 100
Serial Issue: 5A
Title: The assumption of Poisson seismic-rate variability in CSEP/RELM experiments
Affiliation: Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy
Pages: 2293-2300
Published: 201010
Text Language: English
Publisher: Seismological Society of America, Berkeley, CA, United States
References: 22
Accession Number: 2010-093113
Categories: Environmental geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Seismological Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201049
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