Geophysical and geotechnical factors in urban planing: Bursa (Nilüfer, Osmangazi, and Yildirim) cases

The study area covers the Central of Bursa, Osmangazi, Yildirim, Gürsü, Kestel and Nilüfer District boundaries in Bursa. The seismic process deals with the occurrence of an earthquake event and the process of wave propagation from the source to the site. Local amplification caused by surficial soft soils is a significant factor in destructive earthquake motion. In the first phase of this study, it is investigated the ground motion level and soil amplifications for Bursa city. For his aim, probabilistic and deterministic earthquake hazard analysis (including acceleration estimations) will be carried out for the region. Local amplification caused by surficial soft soils is a significant factor in destructive earthquake motion. In the first phase of this study, it is investigated the ground motion level and soil acharacterization for the region. For his aim, probabilistic earthquake hazard analysis (including acceleration estimations) was carried out for the region. Then, soil shear wave velocities were estimated from data obtained by MASW measurements. Soil liquefaction is a natural event in which the strength and stiffness of a soil are reduced by earthquake vibrations or other dynamic loadings. As it is known, liquefaction occurs in saturated soils, that is, soils in which the space between individual particles is completely filled with water. One of liquefaction evaluation methods is based on the cyclic stress approach. In this method, a safety factor is defined as CRR/CSR. CRR is a cyclic resistance ratio that represents soil liquefaction susceptibility, and CSR is the cyclic stress ratio that represents the earthquake effect. In the second phase of this study, possible soil potential index (PL) and ground induced settlements were estimated by using Isihara ve Yoshimine (1990) approach. All results on liquefaction potential index (Pl), liquefaction induced settlements and soil shear wave velocities in Bursa (Turkey) City were compared with each other. Finally, a seismic microzonation map was prepared by the integration of geophysical and geotechnical data for urban planning purposes.

EARTHQUAKE HAZARD ANALYSIS OF NGANJUK REGENCY

Earthquake hazard must be considered by many regions in Indonesia. This is including Nganjuk Regency, the area with intensifies development and where the longest dam in Indonesia is being built. Earthquake hazard studies are conducted using two methods, namely semi-deterministic and probabilistic methods. The results of analyses using the first method show that Nganjuk Regency can be divided into 3 classes of hazards, low level in the southwest region, middle level in the north and high level in the middle of the region. Analyses using the second method reveal that Nganjuk Regency can be classified into two categories, the southwest region which has the potential to experience very strong shocks with an intensity of upper VII MMI to lower VIII MMI and the northern and central region which has the potential of destructive shocks with an intensity of middle VIII MMI. The difference in the results from the two methods can be eliminated by classifying the detail of the existing soil/rock types.

ANALISIS ZONA BAHAYA GEMPABUMI BERDASARKAN METODE DETERMINISTIK DAN PENDEKATAN GEOMORFOLOGI KOTA PADANG SUMATERA BARAT

Research on earthquake hazard analysis based on deterministic methods and the geomorphology approach of Padang City has been carried out to determine the maximum soil acceleration (PGA) and amplification of the source of the Suliti faults and Earthquake Subduction and determine soil classes based on shear waves (Vs30). The PGA value, several attenuation equations are used to find the magnitude of the shock produced when a shallow earthquake occurs. For the source of fault earthquakes, the attenuation equations used are the equivalent of Boore-Atkinson, Campbell-Bozorgnia, and Chiou-Young. While the attenuation equations used to obtain PGA values from subduction earthquake sources are Atkinson-Boore, Youngs, and Zhao. PGA value of earthquake source Subduction in bedrock 0.0374 g. While the PGA value on the surface is 0.0769 g. Whereas the PGA value in the fault source (Hard Fault) in bedrock ranged from 0.0376 g, while the PGA value on the surface ranged from 0.0573 g. Areas that have a severe impact if an earthquake originates from a fault are Koto Tengah District, West Padang Subdistrict, and North Padang Subdistrict with the highest amplification value of 1.7690 ( 9 times) which indicates that the magnification of the area is high. Whereas in the case of an earthquake with an earthquake source subduction area which is very vulnerable is West Padang District, Koto Tengah District, Padang Utara District with an amplification value of 2.0607 ( 9 times).