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All Journal IJOG : Indonesian Journal on Geoscience
Yudhicara Yudhicara
Centre for Volcanology and Geological Hazard Mitigation Geological Agency, Jln. Diponegoro No. 57 Bandung, West Java
Earth & Planetary Sciences

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Characteristics of Paleotsunami Sediments, A Case Study in Cilacap and Pangandaran Coastal Areas, Jawa, Indonesia Yudhicara, Yudhicara; Zaim, Y.; Rizal, Y.; Aswan, Aswan; Triyono, R.; Setiyono, U.; hartanto, D.
Indonesian Journal on Geoscience Vol 8, No 4 (2013)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (2693.2 KB) | DOI: 10.17014/ijog.v8i4.166

Abstract

DOI: 10.17014/ijog.v8i4.166A paleotsunami study having been conducted in 2011 took two study cases in Cilacap and Pangandaran coastal areas. These two regions have been devastated by tsunami in the past and had the most severe damaged on 17 July 2006. Trenching, beach profiling, and sediment sampling had been carried out, and further analysis at the laboratory had been done, such as grain size and fossil analyses and dating. In Cilacap, an iron sand layer was found as a key bed suspected as a paleotsunami deposits due to the content of anthropogenic fragments. In Pangandaran, two layers of tsunami deposit candidates were found having thickness of 5 - 6 cm at the top as a 2006 tsunami deposit candidate, and 5 - 10 cm at the bottom as a paleotsunami deposit candidate. Both grain size and fossil analysis results could explain that Pangandaran’s sediments are tsunami deposits while Cilacap’s ones are assumed to be deposited by another process rather than a tsunami.
Kaitan antara karakteristik pantai Provinsi Sumatera Barat dengan potensi kerawanan tsunami Yudhicara, Yudhicara
Indonesian Journal on Geoscience Vol 3, No 2 (2008)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (820.464 KB) | DOI: 10.17014/ijog.v3i2.51

Abstract

http://dx.doi.org/10.17014/ijog.vol3no2.20084The coast of West Sumatera Province has two types of beaches: low lying sandy beach and steep rocky beach. Straight shoreline beaches at Padang beach until Air Bangis at the north and between Pasir Ganting and Salido beach at the south will have a potential tsunami height lower than bay shape beaches like at Kasai Bay, Kabung Bay, Batung Bay and Nibung Bay. A tsunami inundation will be further at a low lying area (low lying sandy beaches) compared with a coastal area which has steep slope and high relief (steep rocky beaches). Gosong beach at Pariaman which has a steep angle of beach slope will have lower tsunami height compared with a low angle beach slope like at Sungai Beramas, Kasai, Kabung, Batung and Nibung bays which have a beach slope about 3° to 5°. The maximum tsunami inundation is assumed to be located at Pasaman and Pasir Pariaman Sub-regencies, while the maximum tsunami height is assumed to be located at the middle of mapped area which has a bay shape. Tsunami is assumed to be arrived early at the southern most of mapped area or close to Muko-muko (Bengkulu). The maximum height difference from sea level was found at Tabai - Pariaman about 5.394 m, while the minimum height difference was found at Carocok Anau about 1.821 m. The horizontal distance measured from the nearest building from the shoreline is about 119 to 173 m. The worst case of tsunami modeling assumed that the maximum tsunami height will be about 32 m and used for reference to make tsunami prone zonation, such as high, moderate and low prone area.    
Tsunamigenik di Selat Sunda: Kajian terhadap katalog Tsunami Soloviev Yudhicara, Yudhicara; Budiono, K.
Indonesian Journal on Geoscience Vol 3, No 4 (2008)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (797.027 KB) | DOI: 10.17014/ijog.v3i4.64

Abstract

http://dx.doi.org/10.17014/ijog.vol3no4.20086Tsunamigenic is a natural phenomena which is potential to generate a tsunami, such as water dis- turbance due to the presence of activities of volcanism, earthquakes, coastal and sub marine landslidse, or other causal factors . Historically, the Sunda Strait has experienced several tsunami events recorded in the tsunami catalog. Those tsunamies were caused by some geological phenomena such as eruptions of Krakatau submarine volcano in 416, 1883, and 1928; earthquakes in 1722, 1852, and 1958; and other causes which were suggested as a mass failure of coastal and submarine landslide in 1851, 1883, and 1889. Tectonic condition of the Sunda Strait is very complicated, because this region is located at the boundary of Indian-Australian and Eurasian Plates, where a unique island arc system occurs with its association such as trench, accretionary zone, volcanic arc and back-arc basin. Sunda trench as a plate boundary is the most potential region to produce big earthquakes. Existence of a seismic gap in the region can cause a stress accumulation and store energy, then it will be released any time as a big earthquake to generate a tsunami. Along eruption history, Krakatau volcanic arc has four stages of reconstruction and three stages of destruction, and every destruction stage produces tsunami which is suggested to be potentially repeated in the future in a period between 2500 to 2700. Seafloor of the Sunda Strait has an unstable geological condition due to geological structure development, which creates grabens and also enable to produce submarine landslides triggered by earthquake. Coastal condition around the Semangko and Lampung Bays consisting of steep topography with high intensity of weathering, is another factor to contribute landslide, particularly in the case of triggering be heavy rainfall between December to Februari. Furthermore, if landslide materials tumble into the water, even very small and locally, could create a potency of tsunami.  
Tsunami Characteristics along The Coast of Biak Island based on the 1996 Biak Tsunami Traces Yudhicara, Yudhicara
Indonesian Journal on Geoscience Vol 7, No 1 (2012)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (1045.437 KB) | DOI: 10.17014/ijog.v7i1.135

Abstract

DOI: 10.17014/ijog.v7i1.135Identification on tsunami traces had been conducted along the coast of Biak Island, Papua, to recognize the character of tsunami potential in this region, referring to the 1996 tsunami event. This study is to observe the influence of tsunami to the environment and tsunami character itself which can be learned from tsunami deposit. According to the 1996 Biak tsunami run up distributions, it can be observed that the maximum tsunami run up was found at the coast which has an undulating to steep morphology rather than other places which has a relatively flat one. The 1996 Biak Tsunami arrival times were approximately between 10 and 15 minutes, such as at the northern and southern coasts of Biak, except for the western one which is about 1 to 5 minutes. This was influenced by the local bathymetry and another possible source triggering tsunami such as a local submarine landslide. The number of tsunami waves were between 2 and 4, and the second one was usually the highest. Based on a sedimentological analysis, the 1996 tsunami deposit is characterized by the dominant coarse sand, while grain size distribution curve shows a character of transportation process similar to an ordinary beach process dominated by saltation current. The foraminifera fossil content tends to indicate that the tsunami deposit was derived from > 200 m seafloor depth (bathyal zone).
Geothermal System as the Cause of the 1979 Landslide Tsunami in Lembata Island, Indonesia Yudhicara, Yudhicara; Bani, Phillipson; Darmawan, Alwin
Indonesian Journal on Geoscience Vol 2, No 2 (2015)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (2571.987 KB) | DOI: 10.17014/ijog.2.2.91-99

Abstract

DOI:10.17014/ijog.2.2.91-99A tsunami landslide which caused hundreds casualties and lots of damage took place on Lembata Island in 1979. In order to understand the characteristics of the landslide mechanism, a field survey was conducted in 2013 which sampled both the origin soil and landslide material, and the water from hotspring around the landslide site. The physical properties of the soil obtained show that the original soil has dominantly coarser grain than the landslide material (80.5% coarser grain compared to 11.8% coarse grain respectively) which indicates that the soil has become finer and softer. Hot spring analysis indicated that the mineral content of the water was 99.48% SO4. This shows that magmatism processes are involved which caused the soil to become acidic and may have fragilised the system. Results of X-ray Diffraction Mineralogy Analysis (XRD) show that the original soil is composed of minerals of cristobalite, quartz, and albite, while the landslide material consists of clay minerals such as quartz, saponite, chabazite, silicon oxide, and coesite which are typical minerals in a hydrothermal environment. Based on these results, it can be concluded that the area was influenced by an active geothermal system that could be the main source mechanism behind this disastrous event. 
Co-Authors Alwin Darmawan, Alwin Aswan Aswan D. hartanto K. Budiono Phillipson Bani, Phillipson R. Triyono U. Setiyono Y. Rizal Y. Zaim