Integrasi Data Batimetri, Backscatter Multibeam Echosounder, dan Push Core untuk Karakterisasi Dasar Laut Pulau Nias

Abstract

Nias merupakan wilayah pada zona subduksi aktif Sumatra yang memiliki geomorfologi dasar laut dan proses sedimentasi yang kompleks. Penelitian ini bertujuan mengidentifikasi jenis dan sebaran sedimen dasar laut berdasarkan data backscatter Multibeam Echosounder (MBES) serta menganalisis hubungan antara nilai backscatter dan ukuran butir sedimen hasil push core. Data akustik diperoleh menggunakan MBES Kongsberg EM712 dan EM304, sedangkan data sedimen berasal dari 11 sampel push core yang dianalisis menggunakan Mastersizer 2000 dan Gradistat. Hasil penelitian menunjukkan bahwa sedimen dasar laut didominasi oleh fraksi lanau (silt) dengan ukuran butir 5,378 hingga 6,857 f atau 0,009 hingga 0,032 mm. Nilai backscatter berkisar antara -15,45 dB hingga -23,12 dB. Hubungan antara backscatter dan ukuran butir tergolong lemah dengan koefisien determinasi (R²) sebesar 0,224. Hasil ini menunjukkan bahwa respons hambur balik dipengaruhi tidak hanya oleh ukuran butir, tetapi juga oleh kedalaman, transmission loss, frekuensi akustik, dan karakteristik fisik dasar laut. Integrasi data MBES dan push core efektif untuk karakterisasi sedimen dasar laut.

Nias is located within the active Sumatra subduction zone, characterized by complex seafloor geomorphology and sedimentation processes. This study aimed to identify the types and distribution of seafloor sediments using Multibeam Echosounder (MBES) backscatter data and to examine the relationship between backscatter intensity and sediment grain size obtained from push core samples. Acoustic data were acquired using Kongsberg EM712 and EM304 MBES systems, while sediment data were collected from 11 push core samples and analyzed using a Mastersizer 2000 and Gradistat software. The results showed that the seafloor sediments were predominantly composed of silt, with grain sizes ranging from 5.378 to 6.857 f, equivalent to 0.009 to 0.032 mm. Backscatter values ranged from -15.45 dB to -23.12 dB. The relationship between backscatter intensity and grain size was weak, with a coefficient of determination (R²) of 0.224. These findings indicate that backscatter response is influenced not only by sediment grain size but also by water depth, transmission loss, acoustic frequency, and other physical characteristics of the seafloor. The integration of MBES backscatter data and push core samples proved effective for characterizing seafloor sediments.