Analysis of Tsunami Wave Height, Run-up, and Inundation in The Coastal of Blitar and Malang Regency

Indonesia is an archipelago located at the meeting point of 3 tectonic plates which constantly collide over time, the energy due to the collision will accumulate and be able to cause large earthquakes that can generate tsunamis. The island of Java is in the subduction zone of these plates, which causes the southern part of Java to have a high earthquake potential. On April 10, 2021, an earthquake measuring M 6.1 occurred in the south of Blitar and Malang. This earthquake was felt by most of the people of East Java, If the earthquake is large enough, it can cause a tsunami on the southern coast of East Java. Therefore, modeling was carried out using the FLOW module of Delft3D software while using earthquake parameters with a strength of M 9.1 which is the worst possible scenario on the southern coast of East Java. The results of this study indicate the fastest tsunami arrival time is 21 minutes, the highest maximum tsunami height is 20 meters, the highest run-up reaches 17,5 meters, and the furthest inundation reaches 765 meters along the southern coast of Blitar and Malang Regency.

Potential megathrust earthquakes and tsunamis off the southern coast of West Java, Indonesia

High seismicity rates in and around West Java occur as a result of the Indo-Australian plate converging with and subducting beneath the Sunda plate. Large megathrust events associated with this process likely pose a major earthquake and tsunami hazard to the surrounding community, but further effort is required to help understand both the likelihood and frequency of such events. With this in mind, we exploit catalog and phase data sourced from the Agency for Meteorology, Climatology, and Geophysics (BMKG) of Indonesia and the International Seismological Centre (ISC) for the period of April 2009 through July 2020, in order to conduct earthquake hypocenter relocation using a teleseismic double-difference method. Our results reveal a seismic gap to the south of West Java, which is in agreement with a previous GPS study that finds the same region to be a potential future source of megathrust earthquakes. Tsunami modeling was conducted in the region based on two scenarios using sources from the Indonesian National Center for Earthquake Studies, and show that the maximum tsunami height may be up to ~ 8 m. This estimate is approximately half the maximum tsunami height predicted by a previous study in which earthquake sources were derived from GPS data inversion.

Field surveys and numerical modeling of the December 2018 Anak Krakatau volcanic tsunami

<p>We report results of field surveys and numerical modeling of the tsunami generated by the Anak Krakatau volcano eruption on 22 December 2018. We conducted two sets of field surveys of the coastal areas destroyed by the Anak Krakatau tsunami in 26-30 December 2018 and 4-10 January 2020. Field surveys provided information about the maximum tsunami height as well as the most damaged area. The maximum tsunami height was up to 13 m. Most locations registered a wave height of 3-4 m. Tsunami inundation was limited to approximately 100 m. For modeling, we considered 12 source models and conducted numerical modeling. The scenarios have source dimensions of 1.5–4 km and initial tsunami amplitudes of 10–200 m. By comparing observed and simulated waveforms, we constrained the tsunami source dimension and initial amplitude in the ranges of 1.5–2.5 km and 100–150 m, respectively. The best source model involves potential energy of 7.14 × 10<sup>13</sup>–1.05 × 10<sup>14</sup> J which is equivalent to an earthquake of magnitude 6.0–6.1.</p>

Fundamental Study on the Development of a Tsunami Hazard Map for Moored Vessels in a Port

The Great East Japan Earthquake in 2011 revealed the vulnerability of modern ports to damage caused by drifting vessels as a result of a tsunami. The goal of the present study is to develop a tsunami hazard map for moored vessels in order to evaluate the potential for damage caused by drifting vessels that were previously moored at a port. The proposed map consists of four components: a maximum tsunami-height map, a maximum inundation depth map, a maximum flow velocity map, and an evaluation map of maximum mooring tension. The proposed tsunami hazard map for mooring vessels can be used to reduce the number of possible mooring locations and to obtain information for selecting a promising candidate mooring location. Furthermore, information on the tsunami force on moored vessels and on the grounding of vessels by a tsunami can be obtained, and information required for the development of preemptive measures for tsunami relief can be obtained using the proposed hazard map. In the present study, the suitability of mooring locations at Kisarazu port was analyzed, and the results are presented in the form of a map.

KARAKTERISTIK PANTAI DAN RESIKO TSUNAMI DI KAWASAN PANTAI SELATAN YOGYAKARTA

Gempa besar yang terjadi di selatan Jawa yang menimbulkan tsunami pada tanggal 17 Juli 2006, telah menimbulkan dampak kerusakan yang dialami oleh kawasan pantai di selatan Jawa, diantaranya pantai Yogyakarta dengan tinggi maksimum sekitar 3,4 meter. Gempa ini mempunyai magnitude M7,7 (USGS, 2006), pada kedalaman 10 km di bawah dasar laut. USGS menyatakan bahwa gempa ini memiliki mekanisme sesar naik dan berasosiasi dengan zona subduksi antara lempeng Indo-Australia dan lempeng Eurasia. Hasil penelitian terdahulu yang dilakukan oleh Pusat Penelitian dan Pengembangan Geologi Kelautan pada tahun 2002 memperlihatkan bahwa kondisi batimetri di perairan selatan Yogyakarta dari pantai hingga 12 mil ke arah laut lepas berkisar antara 5 hingga 350 meter, yang berangsur makin dalam ke arah laut dengan pola kontur batimetri yang sejajar dengan garis pantai. Berdasarkan karakteristik pantainya, kawasan pantai Yogyakarta dapat dibagi menjadi 2 zona resiko tsunami, yaitu: (1) Zona Resiko Tinggi terdapat pada lokasi dengan bentuk pantai berteluk dan pantai berkantong (pocket beach) di kawasan sepanjang pantai mulai dari Parangendog ke arah timur hingga pantai Sadeng, khususnya pada pantai-pantai yang dimanfaatkan sebagai kawasan wisata atau pemukiman nelayan yang dibangun relatif dekat dengan garis pantai; (2) Zona Resiko Rendah, diperlihatkan di kawasan sepanjang pantai mulai dari Parangtritis ke arah barat hingga pantai Pasir Congot, yang meskipun memiliki morfologi pantai relatif landai dengan garis pantai lurus, namun pemukiman dan bangunan wisat dibangun pada jarak yang relatif jauh dari garis pantai dan berada di belakang gumuk pasir (sand dune) yang berfungsi sebagai pelindung alami dari gelombang tsunami. Kata kunci : tsunami, karakteristik pantai, batimetri, zona resiko tsunami Great earthquake that has generated tsunami occurred offshore south of Java in July 17, 2006. The coast of Yogyakarta was one of the impacted areas by tsunami waves and the maximum tsunami height measured in this area about 3.4 meters. This earthquake has Magnitude M 7.7 (USGS, 2006) with depth of about 10 kms under the seafloor. USGS pointed out that this earthquake was thrust fault mechanism associated with subduction zone between Indo-Australia and Eurasian Plates. Study on marine and coastal geology at the coast of Yogyakarta has been carried out by Marine Geological Institute in 2002. Based on this study, it was known that bathymetry along the coast as far as 12 miles seaward are about 5 meters to 350 meter-depth which are gradually increase contour parallel to the shoreline. Coastal characteristic study along the coast of Yogyakarta indicate that this area can be divided into two zones of tsunami risk; (1) First zone is high tsunami risk, which is represented by coastal area along Parangendog to Sadeng, this area is bay-shape, settlement area generally close to the shoreline without sufficient protection; (2) Flat morphology, with sand dune along Parangtritis to the west, dominated by straight shoreline, and settlement area behind the sand dune, make this area has relatively low in tsunami risk. Keywords: tsunami, coastal characteristic, bathymetry, tsunami risk zone.

PROBABILISTIC TSUNAMI HAZARD ANALYSIS AND RISK TO COASTAL POPULATIONS IN THAILAND

The study of tsunami hazards in Thailand has been an ongoing topic of research. However, the hazards from tsunami sources based on probabilistic study and population risk are still unclear. In this study, potential tsunami sources along rupture zones were selected. A series of far-field tsunami simulations were performed with scaled fault parameters based on fault lengths from 100–600 km. The results show that within a few centuries, the maximum tsunami height could be 2–5 m at the west coast and less than 2 m at the east coast. The potential tsunami exposure (PTE) of populations in an estimated inundation zone was calculated using global population data in relation to tsunami height. The results show that much attention should be paid to fault ruptures longer than 300 km (≈ 8.5 moment magnitude, Mw) that originate from 4°–6° N and 14°–17° N for the Sumatra subduction zone and the Manila trench, respectively. A quarter of a million people are at risk of exposure to a maximum 9 m tsunami height after 100 min of the arrival of the first wave at the Andaman coast. One million people near the Gulf of Thailand are at risk of a tsunami height less than 3 m after 9 hr.

The 1867 Virgin Island Tsunami

The 1867 Virgin Island Tsunami reached large magnitude on the coasts of the Caribbean Islands. A maximum tsunami height of 10 m was reported for two coastal locations (Deshaies and Sainte-Rose) in Guadeloupe. Modelling of the 1867 tsunami is performed in the framework of the nonlinear shallow-water theory. The directivity of the tsunami wave source in the Caribbean Sea according to the assumed initial waveform is investigated. The tsunami records at the several coastal regions in the Lesser Antilles, Virgin Islands, Puerto Rico and South America are simulated. The comparison between the computed and observed data is in reasonable agreement.