[S-SS05] Natural hazards and uncertainty: Informing societal decisions

[SSS05-P02] Seismic Source Charaterisation for PSHA in the Solomon Islands

*Calvin Luiramo Qwana¹, Shinichi Matsushima¹ (1.Graduate School of Architecture and Architectural Engineering, Kyoto University)

Keywords:Solomon Islands, Active faults, Seismic source zones segments, Seismic source characterization, Tectonic movements, Geological tectonics

Characterizing seismic sources in the region plays a dominating role in the outcome of Probabilistic Seisimic Hazard Analysis (PSHA) studies. As such, a reliable estimation of source characteristics such as the magnitude range, spatial and temporal distribution for seismic events in the region of the Solomon Islands is necessary, as the region where information on active faults and other geologic structures is generally limited. This present study focus on the seismic source characterization for Solomon Islands, by identifying the potential seismic source as finite fault sources in the subduction zones and the transition zone as the plate boundaries between the Indo-Australian plate and the Pacific plate, as well as the seismic source zones of background seismicity within the studied area bounded by 153 degrees East to 168 degree East and 3 degree South to 13 degree South (Fig.1). The region is known for its tectonic complexicity features, geology, high rate of tectonic plate movement and presence of doublet earthquakes of large magnitudes that greater than or equal to M7. Since 1946, the area has experienced 55 earthquakes of earthqauke greater than or equal to M7, of which 15 were doublet events. To account for such rate of seismicity for the study region, earthquake characteristics recurrence model is developed for the probability density function on magnitude and different slip rate to estimate the earthquake occurrence rates. The seismotectonic region is divided into four seismic source zones segments: namely (i) the Bougainville Segment, (ii) the New Georgia, (iii) the Guadalcanal-Makira Segment and (iv) the Santa-Cruz segment. Earthquake catalogues for each source zone segments are analysed for completeness of magnitude and time. The seismic parameter b for the seismogenic segments are then estimated using a maximum likelihood method, and the mean annual activity rate, maximum possible magnitude, for the four seismic segements are estimated. The estimated b values are then used to evaluate the seismicity activity in the segments. The result of this study of characterizing the finite faults of magnitude greater than or equal to M7 and background seismicity from each of the four seismic source zones will later be incorporated into PSHA for the Solomon islands to understand the level of potential hazard and post the likely level of seismic risk for the future in these islands.