Regional Ground Motion Model Evaluation for the Southern Eastern African Rift System
Description:
Current seismic hazard assessments in the southern East African Rift System (EARS) use ground motion models (GMMs) developed from global datasets. Considering the region’s early-stage continental rift setting combined with a deep seismogenic zone, it is unclear whether these models can predict the expected ground motion levels accurately. Both seismically vulnerable communities and faults with the potential to host magnitude (M) 7-8 earthquakes are located within this tectonically active region, resulting in a significant seismic risk. We explore the available ground motion records from earthquakes along the eastern and western branches of EARS to assess the suitability of the global GMMs commonly used, with particular focus on focal depths of the earthquakes and ground motions at close distances, and adapt selected GMMs to obtain a regional GMM.
First, we compile a ground-motion database of earthquakes that is critically lacking for the southern EARS. This database includes a regional catalog of 882 earthquakes since 1980 (M 3 to 6.5) with available waveform records within epicentral distances of 300 km. For accurate calculations of earthquake locations (including focal depths), we relocate 250 events down to depths of 35-40 km. Data are scarce for events larger than M 5, especially at distances less than 100 km. Next, we find that ground motions are generally overestimated at close distances (<100 km) by the global GMMs, especially at shorter oscillator periods and peak ground acceleration. Finally, we use the referenced empirical approach and mixed-effects regression to obtain a regional GMM for southern EARS. This work provides valuable input to be used in future seismic hazard assessments for the region, producing a relocated earthquake catalogue and a much-needed regional GMM, to better understand the spatial distribution of earthquakes, examine tectonic EARS processes with depth, and quantify the expected ground motion levels.
Session: Advances in Probabilistic Seismic Hazard Analysis and Applications [Poster]
Type: Poster
Date: 4/20/2023
Presentation Time: 08:00 AM (local time)
Presenting Author: Joanna M. Holmgren
Student Presenter: No
Invited Presentation:
Authors
Joanna Holmgren Presenting Author Corresponding Author joanna.holmgren@bristol.ac.uk University of Bristol |
Maximilian Werner max.werner@bristol.ac.uk University of Bristol |
Katsuichiro Goda kgoda2@uwo.ca University of Western Ontario |
Manuela Villani manuela.villani@arup.com Arup Group Ltd |
Vitor Silva vitor.silva@globalquakemodel.org Global Earthquake Model |
Patrick Chindandali rafikiwanga@gmail.com Malawi Geological Survey |
Victoria Stevens victorialouise.s@ntu.edu.sg Earth Observatory of Singapore, Nanyang Technological University |
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Regional Ground Motion Model Evaluation for the Southern Eastern African Rift System
Category
Advances in Probabilistic Seismic Hazard Analysis and Applications