Juan Pandu Gya Nur Rochman

Pemodelan 3D Kecepatan Gelombang P Dengan Metode Double Difference Dan Tomografi Travel Time Untuk Identifikasi Patahan (Studi Kasus Patahan Palu- Koro)

Central Sulawesi is one of earthquake-prone areas in Indonesia. The source of the earthquake comes from an active fault in Central Sulawesi, one of which is the Palu-Koro Fault. This research was conducted to determine 3D model of P wave velocity and to know the fault zone in research area by using double difference method and travel time tomography by utilizing local earthquake data. The result of hypocenter relocation by double difference method using hypo DD program is vertical cross section which pass Palu-Koro fault indicates the depth of the fault is about 3-27 km. Coupled Velocity Hypocenter method using Velest 3.3 program was done in this research to obtain 1D model of P wave velocity. The 1D model of P wave velocity generated in this study is the value of velocity between 3.28 km/s up to 9,07 km/s at depth range 0-36 km. The 3D model of the P wave velocity shows a speed value between 5 km/s up to 9 km/s in the area through which raytracing is passed. Hypocenter relocation by double difference method has a tendency gather forming clusters that can be indicated as fracture around the cluster. The 1D model of P wave velocity increased value on several layers. The 3D model of P wave velocity shows raytracing passing the fastest path and has a high velocity associated with magmatic rock saround the Palu-Koro fault.

Assessment of Sidoarjo mud flow embankment stability using very low frequency electromagnetic method

The earth on LUSI embankment has a high failure potential due to several factors such as: seepage, leakage, vertical and horizontal deformation, cracking and fault (discontinuity), overtopping, mud slide, and swelling. Very low frequency electromagnetic method was carried out at LUSI embankment in order to delineate fracture and potential pathway of seepage occurring through the subsurface structure the embankment body. To reach these objectives, several methods were carried out in the selected area, such as direct current resistivity, total station and Rayleigh wave dispersion to provide information on the mechanical properties LUSI embankment subsurface. This study indicates that seepage and fracture through the LUSI embankment is presented by a set of lines which are possibly caused by deformation in the LUSI area. Furthermore, based on the fracture and seepage positions and mud or fluid flow direction, the unstable LUSI embankment is determined as located around the northwest and northern parts of the area.