Publication Date:
2017-04-04
Description:
The Asperity Likelihood Model (ALM), first developed and currently tested for California, hypothesizes that
small-scale spatial variations in the b-value of the Gutenberg and Richter relationship play a central role in forecasting
future seismicity (Wiemer and Schorlemmer, SRL, 2007). The physical basis of the model is the concept
that the local b-value is inversely dependent on applied shear stress. Thus low b-values (b 〈 0.7) characterize the
locked paches of faults –asperities- from which future mainshocks are more likely to be generated, whereas the
high b-values (b 〉 1.1) found for example in creeping section of faults suggest a lower seismic hazard.
To test this model in a reproducible and prospective way suitable for the requirements of the CSEP initiative
(www.cseptesting.org), the b-value variability is mapped on a grid. First, using the entire dataset above the
overall magnitude of completeness, the regional b-value is estimated. This value is then compared to the one
locally estimated at each grid-node for a number of radii, we use the local value if its likelihood score, corrected
for the degrees of freedom using the Akaike Information Criterion, suggest to do so.
We are currently calibrating the ALM model for implementation in the Italian testing region, the first region
within the CSEP EU testing Center (eu.cseptesting.org) for which fully prospective tests of earthquake
likelihood models will commence in Europe. We are also developing a modified approach, ‘hybrid’ between a
grid-based and a zoning one: the HALM (Hybrid Asperity Likelihood Model). According to HALM, the Italian
territory is divided in three distinct regions depending on the main tectonic elements, combined with knowledge
derived from GPS networks, seismic profile interpretation, borehole breakouts and the focal mechanisms of the
event. The local b-value variability was thus mapped using three independent overall b-values. We evaluate the
performance of the two models in retrospective tests using the standard CSEP likelihood test.
Description:
Unpublished
Description:
Vienna
Description:
3.1. Fisica dei terremoti
Description:
open
Keywords:
ALM model
;
HALM model
;
04. Solid Earth::04.06. Seismology::04.06.02. Earthquake interactions and probability
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
Poster session
Permalink
