PENCITRAAN STRUKTUR HALUS TERMOHALIN MENGGUNAKAN SEISMIK REFLEKSI MULTIKANAL DI UTARA LAUT MALUKU

Abstract

Low-frequency acoustic such as marine seismic that has been commonly used in geological mapping is nowadays being developed as tools to map the water columns. This study aims to map thermohaline fine structure in the Northern Maluku Sea. Seismic reflection data from 72 channel along 239 km track line was processed to delineate water column structure. The depth-distance seismic oceanography section clearly showed reflectors at depth of 400 m and 800 m correspond to lower boundary of the seasonal and permanent thermocline layers, respectively. The reflections between depth of 400 m and 800 m were caused by the thermohaline staircase as confirmed by CTD data. Water column reflections showed the presence of internal wave-like structure in the northwestern Tufure sill which has height and wavelength about 102 m and 17 km, respectively. The seismic amplitude in the water column corresponded to the vertical contrast of physical oceanographic parameters such as temperature, salinity, and sound speed. Reflections in the water column could be caused by temperature gradients ranging contrast from 0.03°C/m to >0.20°C/m. The acoustic impedance in the internal wave-like zone was ranging from 0.8 x 106 kg/m3 m/s to 2.06 x 106 kg/m3 m/s. This research revealed that the marine seismic data can be useful for studying the water column characteristics in the Northern Maluku Sea.