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RISE in brief

Earthquakes are the deadliest natural hazard. Developing tools and measures to reduce future human and economic losses is the aim of RISE. RISE stands for Real-time earthquake rIsk reduction for a reSilient Europe and is a three-year project financed by the Horizon 2020 programme of the European Commission. It started in September 2019 and will end in February 2023. RISE is coordinated by ETH Zurich, it brings together 19 organisations from across Europe and five international partners.

News

2021-12-15

How well does poissonian probabilistic seismic hazard assessment (PSHA) approximate the simulated hazard of epidemic‐type earthquake sequences?

Shaoqing Wang and Max Werner from the University of Bristol published new research that challenges basic assumptions of standard seismic hazard assessment. Classical Poissonian probabilistic seismic hazard assessment (PSHA) relies on the rate of independent mainshocks to estimate future seismic hazard levels. Real earthquakes, however, cluster in time and space. This article shows that classical PSHA only poorly approximates hazard levels implied by models of more realistic clustered seismicity, such as the Epidemic Type Aftershock Sequences (ETAS) model.

The work also compared ETAS-implied hazard with Sequence-based PSHA (SPSHA) and found much better agreement, although none of the approximate methods could reproduce the multiple exceedance curves implied by the ETAS model. This suggests that cumulative seismic risk assessment with damage‐dependent fragility curves might need to consider ETAS‐like sequences.

Shaoqing Wang and Max Werner also investigated the relation between short‐term (conditional) and long‐term hazard and proposed a hazard analog of the Omori-Utsu and Utsu-Seki scaling laws as a function of initial magnitude, elapsed time, and long‐term hazard. This model can provide a quick prediction of ensemble‐averaged short‐term hazard and the time needed for the hazard levels to return to the long‐term average.

The authors conclude that realistic multigenerational earthquake clustering has both obvious and more subtle effects on long‐ and short‐term hazard and should be considered in refined hazard assessments.

How Well Does Poissonian Probabilistic Seismic Hazard Assessment (PSHA) Approximate the Simulated Hazard of Epidemic‐Type Earthquake Sequences? Shaoqing Wang; Maximilian J. Werner; Ruifang Yu. Bulletin of the Seismological Society of America (2021); https://doi.org/10.1785/0120210022 

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