Evaluation of Shallow Crustal Ground Motion Models for West Nusa Tenggara Region, Indonesia

This work evaluates ten GMMs from the complex Next Generation Attenuation (NGA) and earlier simpler models based on ground motion dataset in NTB. Root mean square error (RMSE) and Euclidean distance-based ranking (EDR) were employed to assess the suitability of the GMMs to the observed data. The results indicate that CY08 and NGA-West2 models are most appropriate for NTB. However, investigation on the total residuals revealed that the GMMs still have considerable differences and variability. To address these issues, this study proposes a model adjustment using an additional term. The proposed model has significantly improved performance over all GMMs considered. Findings demonstrate that the proposed GMM fits the recorded acceleration response spectra of the 5 August 2018 M_w 6.9 event at periods longer than 0.3 s. At shorter periods, our study reveals that the response spectra of the 19 August 2018 event exceed the existing national spectra design, highlighting the urgency of updating the spectra design for the NTB region in the near future. The ground motion parameters predicted by the adjusted model are crucial for seismic hazard analysis and subsequent geological hazard assessments in the NTB region.