International audienceWe present results from multibeam bathymetric data acquired during 2005 and 2006, in the region of maximum slip of the 26 Dec. 2004 earthquake (Mw 9.2). These data provide high-resolution images of seafloor morphology of the entire NW Sumatra forearc from the Sunda trench to the submarine volcanic arc just north of Sumatra. A slope gradient analysis of the combined dataset accurately highlights those portions of the seafloor shaped by active tectonic, depositional and/or erosional processes. The greatest slope gradients are located in the frontal 30 km of the forearc, at the toe of the accretionary wedge. This suggests that long-term deformation rates are highest here and that probably only minor amounts of slip are accommodated by other thrust faults further landward. Obvious N–S oriented lineaments observed on the incoming oceanic plate are aligned sub-parallel to the fracture zones associated with the Wharton fossil spreading center. Active strike-slip motion is suggested by recent deformation with up to 20–30 m of vertical offset. The intersection of these N–S elongated bathymetric scarps with the accretionary wedge partly controls the geometry of thrust anticlines and the location of erosional features (e.g. slide scars, canyons) at the wedge toe. Our interpretation suggests that these N–S lineaments have a significant impact on the oceanic plate, the toe of the wedge and further landward in the wedge. Finally, the bathymetric data indicate that folding at the front of the accretionary wedge occurs primarily along landward-vergent (seaward-dipping) thrusts, an unusual style in accretionary wedges worldwide. The N–S elongated lineaments locally act as boundaries between zones with predominant seaward versus landward vergence
Perairan Teluk Banten merupakan wilayah yang sibuk dengan aktivitas wisata bahari, industri, permukiman dan lain-lain. Kondisi tersebut dapat menimbulkan dampak-dampak negatif seperti pencemaran, erosi, dan masalah lingkungan lainya. Pemahaman mengenai kondisi hidro-oseanografi sangat penting sebagai langkah untuk pengelolaan dan perlindungan wilayah pesisir dan laut. Tujuan dari penelitian ini untuk mengetahui karakteristik hidrodinamika di Perairan Teluk Banten pada musim peralihan (Agustus - September) berdasarkan data primer (data satu bulan arus, pasang surut, suhu) dan data sekunder (batimetri, kualitas air dan nutrient). Simulasi model diolah menggunakan MIKE 21, didukung dengan penggunaan CD-Oceanography. Hasil pengolahan data menunjukkan bahwa pola arus di Perairan Teluk Banten didominasi arus pasut dengan kecepatan berkisar antara 0-0,41 m.s-1, ditunjukkan oleh hasil pengolahan dalam bentuk stick diagram dan scatter plot yang menunjukkan pergerakan arus cenderung teratur dan arah arus dominan menuju ke arah Tenggara dan Selatan, hal ini juga didukung dengan hasil Current rose dengan menggunakan software WR plot. Kecepatan arus di permukaan lebih besar dan menyebar dibanding kecepatan arus di dekat dasar perairan. Simulasi arus permukaan (nilai error MRSE 12,25 %) menunjukkan bahwa arus bergerak sesuai dengan pengaruh pasang dan surut dengan kecepatan berkisar antara 0-0,42 m.s-1. Simulasi juga memperlihatkan distribusi konsentrasi nutrient dan kualitas perairan dipengaruhi oleh karakteristik hidrodinamika Teluk Banten.
The use of coastal forests as natural tsunami barrier has long been the source of controversies due to inconclusive understanding on the damping performance and contradictory field findings from the last tsunami events. After experiencing hundreds of casualties and severe destruction on the infrastructures due to the 2006 South Java Tsunami, the coastline of Pangandaran district in West Java was replanted by coastal forest vegetation to mitigate future tsunami as well as improving the quality of the environment. The design of coastal forests along the coastline of Pangandaran adopted divide-and-rule strategy concept. Considering their physical and biological aspects as well as the ability to withstand hydraulic forces. This concept requires different species at different locations perpendicular to the coastline with staggered formations in order to provide optimum damping performance of the coastal forests. Unfortunately, this concept has never been quantified or hydraulically tested against extreme cases like tsunami. The paper will present the characteristics and the latest conditions of coastal forests in Pangandaran including the problems and the challenge of this mitigation system in the last five years. Moreover, damping performance of the coastal forests was also investigated by means of Nonlinear Shallow Water Equation Model to quantify the contribution of coastal forest and other existing environmental aspects such as the bathymetry and the topography to the total tsunami attenuation. Based on the obtained wave transmission, the simulation analysis shows that the
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