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- Study of the 24 September 2013 Oman Sea tsunami using linear shallow water inversionPublication . Baptista, Maria Ana Carvalho Viana; MIRANDA, JORGE MIGUEL; Omira, Rachid; El-Hussain, IssaIn this study, we present a linear inverse approach for the computation of the initial water displacement of a tsunami. The method uses empirical Green functions and linear shallow water wave theory. We apply this methodology to study the source of the 24 September 2013 tsunami off the Makran coast. We re-analyze the 2013 tsunami data, particularly the tide records in the coast of Oman and the DART buoy record in the Arabian Sea, to infer its source. We use wavelet and Fourier analyses to characterize the frequency content of the tide records and the possible influence of local harbor effects. We compute empirical Green functions for the possible source area, and then use a linear shallow water inversion technique to assess the water disturbance in the early stage of tsunami propagation. The comparison between forward modeling and observations shows a fair agreement with available data, particularly in what concerns the DART record. It also suggests the existence of local amplifications in a number of Omani harbors. The free surface elevation obtained by inversion of the waveforms is coherent with a landslide located close to 61.5 degrees E, 24 degrees N, sliding to the S or SSE direction. Our results show that the inversion technique used here leads to a better characterization of the tsunami source than the simple backward ray tracing which assumes a simple point source. In addition, these results strengthen the hypothesis that landslides might have played an important role in previous tsunami events in the area, and must be taken into account for tsunami hazard assessment on the Omani coast.
- Probabilistic and deterministic estimates of near-field tsunami hazards in northeast OmanPublication . El-Hussain, Issa; Omira, Rachid; Al-Habsi, Z.; Baptista, Maria Ana Carvalho Viana; Deif, A.; Mohamed, A. M. E.Tsunamis generated along the Makran subduction zone (MSZ) threaten the Sur coast of Oman, according to deterministic and probabilistic analyses presented here. A validated shallow water numerical code simulates the source-to-coast propagation and quantifies the coastal hazard in terms of maximum water level, flow depth, and inundation distance. The worst-case source assumed for the eastern MSZ is a thrust earthquake of Mw 8.8. This deterministic scenario produces simulated wave heights reaching 2.5m on the Sur coast leading to limited coastal inundation extent. Because Oman adjoins the western MSZ, the probabilistic analysis includes the effect of this segment also. The probabilistic analysis shows onshore inundations exceeding 0.4km northwest of Sur where flow depths are likely to exceed 1m in 500years. Probability analysis shows lesser inundation areas with probability of exceeding 1m flow depth up to 80% in 500-year exposure time. Teletsunamis are excluded from these analyses because far-field waves of the 2004 Indian Ocean tsunami did not impact the Sur coast. Also excluded for simplicity are tsunamis generated by submarine slides within or near MSZ rupture areas. The results of this research provide essential information for coastal planning, engineering and management in terms of tsunami hazard and an essential step toward tsunami risk reductions in the northwest Indian Ocean.
- Probabilistic tsunami hazard assessment along Oman coast from submarine earthquakes in the Makran subduction zonePublication . El-Hussain, Issa; Deif, Ahmed; Omira, Rachid; Al-Habsi, Zaid; Al-Rawas, Ghazi; Mohamad, Ade; Al-Jabri, Khalifa; Baptista, Maria Ana Carvalho VianaThe Sultanate of Oman is among the Indian Ocean countries that were subjected to at least two confirmed tsunamis during the twentieth and twenty-first centuries: the 1945 tsunami due to an earthquake in the Makran subduction zone in the Sea of Oman (near-regional field tsunami) and the Indian-Ocean tsunami in 2004, caused by an earthquake from the Andaman Sumatra subduction zone (far - field tsunami). In this paper, we present a probabilistic tsunami hazard assessment for the entire coast of Oman from tectonic sources generated along the Makran subduction zone. The tsunami hazard is assessed taking into account the contribution of small-and large-event magnitudes. Results of the earthquake recurrence rate studies and the tsunami numerical modeling for different magnitudes were used through a logic-tree to estimate the tsunami hazard probabilities. We derive probability hazard exceedance maps for the Omani coast considering the exposure times of 100, 250, 500, and 1000 years. The hazard maps consist of computing the likelihood that tsunami waves exceed a specific amplitude. We find that the probability that a maximum wave amplitude exceeds 1 m somewhere along the coast of Oman reaches, respectively, 0.7 and 0.85 for 100 and 250 exposure times, and it is up to 1 for 500 and 1000 years of exposure times. These probability values decrease significantly toward the southern coast of Oman where the tsunami impact, from the earthquakes generated at Makran subduction zone, is low.