<p>Due to the existence of the megathrust, south of Sunda Strait potentially generate the powerful earthquake and tsunami. It may impact to South of Java Island and Sunda strait coastal zone. One of the city that may impacted by the earthquake and tsunami is the Cilegon city located in the north-east of Sunda Strait. The city is the strategic area which has industrial estate, critical infrastructures, as well as a tourist destination. The earthquake and tsunami hazard may followed by the collateral hazard. 78 petrochemicals factory as well as steel industry, and other national vital object such as electric stream power plant could give a contribution to the industrial hazard.</p><p>Based on a seismological study, the maximum magnitude estimated in megathrust zone Sunda Strait is M 8.7. The existing of active faults and active volcano of Krakatau in Sunda Strait add a complexity of earthquake and tsunami potential in the area. According to historical documentation, there are destructive earthquake associated to south of Sunda Strait megathrust such as West Java earthquake (January 5, 1699), Batavia earthquake (January 22, 1780), Jakarta Earthquake (February 23, 1903), and destructive tsunami associated to the Krakatau eruption (August 27, 1883).</p><p>This study aims to assess the multi hazard potential generated by the megathrust earthquake in the south of Sunda Strait. We simulate the worst case earthquake scenario on the south of Sunda Strait megathrust zone, located at 7.53 S;104.04 E, with 10 km fixed depth. Both simulation of earthquake shakemap and tsunami inundation were carried out in this study.</p><p>The modeling of earthquake indicates ground shaking possibly generates VI-VII MMI in Cilegon. Moreover, the inundation tsunami modeling estimated there are 4 sub-regencies of industrial estate (Ciwandan, Citangkil, Gerogol, and Pulomerak) will be impacted. The highest tsunami inundation may approximately reach 9 m hit a critical infrastructure of the Merak harbor. The maximum distance of tsunami penetration is estimated to be 1.5 km from the coastal line.</p><p><strong>Keywords:</strong> earthquake and tsunami potential, multi collateral hazard, industrial estate, cilegon city, critical infrastructure</p>
<p>Tsunami risk in Indonesia is strongly real and needs serious handling. Due to the extremely dangerous, it is important for coastal communities to be prepared and responsive in responding to threats. The recent decade tsunami disaster highlighted the extraordinary gaps and challenges on the development and strengthening of the downstream component on the system. Communities need to be educated, aware and ready to respond to warnings both natural as well as official warnings. For this reason, the Indonesia Agency for Meteorology, Climatology, and Geophysics (BMKG) considers to introduce an Indonesia Tsunami Ready programme that will encourage communities to build, strengthen and develop their capacity and ability to respond to tsunami threats.</p><p>In this paper we try to analyze the community actualization on hazard assessment, preparedness, and response as the result of the Indonesian Tsunami Ready programme. The assessment is based on the 12 indicators of the tsunami ready which had been determined by the United Nations Educational, Scientific and Cultural Organization-the Intergovernmental Oceanographic Commission (UNESCO-IOC). A field survey of the 12 indicators has been carried out to assess seven communities (Penggarangan, Pangandaran, Gelagah, Kemandang, Tambakrejo, Kuta Mandalika, and Tanjung Benoa) living in the tsunami prone area.</p><p>Generally, the results showed the communities didn&#8217;t have the updated tsunami hazard map as the hazard assessment indicator. The previous hazard map was not established based on the latest seismological study and tsunami modelling. Most of communities have an emergency operation plan for earthquake and tsunami, even though it doesn&#8217;t consider the earthquake information and tsunami warning. In some villages such as Tanjung Benoa and Kuta Mandalika, local potentials are used also to empower the preparedness and response capacity.</p><p>BMKG gave an advocacy to complete and accomplish some the unavailable indicators such as tsunami hazard map, emergency operation plan, and public education materials. The result of this study is expected to be an effective way to build a community awareness, preparedness and response.</p><p><strong>Keywords:</strong> tsunami ready, 12 indicators of tsunami ready, hazard assessment, preparedness, response</p>
On 9 January 2022, two shallow earthquakes occurred in the east arm of Halmahera, Indonesia, with magnitudes of Mw 5.2 and 5.4 felt at III–V modified Mercalli intensity. The existence of the causative fault for the earthquakes was unknown. One possible explanation is that the earthquakes were caused by the activity of an inactive fault striking in the southeast–northwest direction, and possibly linked to the volcanic activities in Halmahera. Thus, further analysis of their characteristics is crucial to identify the previously an inactive fault. In this study, we relocated the associated earthquake hypocenters using the double-difference method with an updated velocity model, and determined the focal mechanisms by employing full waveform inversion using moment tensor analysis. The focal parameters were used to analyze the static stress changes. The relocated hypocenters show specific hypocenter clusters, aligning in the north–south direction, associated with left-lateral faulting mechanisms. This north–south alignment differs from the northeast–southwest trend of some other active faults in Halmahera. We propose that the newly found Tobelo fault dips at an angle of around 80° to the west. The seismic stress change from the mainshock and the foreshock of the Tobelo earthquakes corresponds with the distribution of the aftershocks. A detailed analysis of unidentified faults in the high seismicity area is essential to comprehend the tectonic study of Halmahera Island and its seismic hazard assessments.
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