Heiti verkefnis : 

Eðlisfræðilegt endurmat jarðskjálftavár á brotabelti Suðvesturlands

Verkefnastjóri : 

Benedikt Halldórsson

Stutt lýsing á verkefninu:

The strongest earthquakes in Southwest Iceland take place in the South Iceland Seismic Zone (SISZ), characterized by its unique array of bookshelf strike-slip faults. Recently, the bookshelf fault system has been shown to be all along the Reykjanes Peninsula Oblique Rift zone (RPOR) as well. This reveals that the entire capital region and lifelines of our modern society are in much greater proximity to large bookshelf faults. The Icelandic National Annex for Eurocode 8 is the probabilistic seismic hazard assessment (PSHA) map of Iceland. Due to the above, a comprehensive revision is now needed of the PSHA for Southwest Iceland, but also because past PSHA studies are not only outdated, but they suffered from several and significant limitations. Fortunately however, our intense research efforts over the last few years have addressed all of those limitations. Most relevantly, a new physics-based earthquake fault model has been developed for the transform zone of SISZ-RPOR that not only specifies where the earthquake faults are, but predicts long-term seismicity rates that are fully consistent with the Icelandic historical catalogue. Also, several new state-of-the-art Bayesian hybrid GMMs have been developed for Iceland that now, for the first time, account for key geological types of Iceland (hard/old rock, rock, lava vs. soft soil), and a new backbone approach to PSHA has been developed that treats uncertainties more comprehensively. In addition, two projects in 2019-2022 (the EU-H2020, ChEESE and the Rannís project, SENSHAZ) have produced huge datasets of synthetic physics-based earthquake ground motions from earthquakes in the transform zones. This now lays the foundation for the first comprehensive and state-of-the-art physics-based PSHA for Southwest Iceland, with high resolution of the near-fault hazard in particular. This project will revise the PSHA of Southwest Iceland that will contribute to the new Icelandic National Annexes for Eurocode 8.

Tilgangur og markmið:

The objective (i.e., long-term, to be realized 2-5 years after the project's completion) of this study is to improve the mitigation of the destructive impacts of future earthquakes in Iceland through the comprehensive revision of PSHA for Iceland using new state-of-the- art models, methods, and earthquake source zonation. Moreover, this will include the implementation of the first physics-based approach to PSHA (PB-PSHA), with focus on the earthquake near-fault region of Southwest Iceland. Therefore, the purpose (i.e., short-term, available immediately upon the project's completion) of this specific proposal is to carry out a comprehensive PSHA using Monte Carlo simulations of finite-fault earthquake rupture using a new and complete physics-based earthquake source model of the SISZ-RPOR. For this purpose, the following distinct research topics will be addressed and project results produced: (1) Ranking different GMMs for Peak Ground Acceleration (PGA) and Pseudo-Spectral Acceleration (PSA) that are consistent with Icelandic earthquake data and select the best GMM as the backbone model for use in PSHA; (2) Producing new hazard maps for PGA and PSA at different periods and for different hazard levels using finite-fault earthquake catalogues; (3) Performing the disaggregation of the seismic hazard to identify hazard-dominating events; (4) Producing new hazard uncertainty maps, thus explicitly exposing how our lack of knowledge and the inherent uncertainties affect the overall hazard estimates. (5) Comprehensive comparisons of the results of this study with past PSHA results, both domestic and international results (6) Proposing a new Icelandic National Annex for Eurocode 8. These research topics cumulatively will construct the project's purpose, thus facilitating its objective.