Claim Missing Document
Check
Articles

Found 4 Documents
Search

PRELIMINARY EVALUATION OF LOCAL SITE CONDITON IN YOGYAKARTA BASIN Tun Naing; Subagyo Pramumijoyo; Hiroshi Kawase
Journal of Applied Geology Vol 1, No 1 (2009)
Publisher : Geological Engineering Department Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (461.218 KB) | DOI: 10.22146/jag.7223

Abstract

The Yogyakarta Basin can be defined as NE – SW elongated depression zone of 20 km in width and 45 km in length, trending from Yogyakarta City in north to the Indian Ocean in south. The local geologic and soil conditions have a great influence on the intensity of ground motion and earthquake damage. Local site effects play an important role in earthquake-resistant design and must be accounted for on a case by case basis. Local site conditions can profoundly influence all of the important characteristics such as amplitude (peak acceleration, velocity and displacement), frequency content and duration of strong ground motion. The extent of their influence depends on the geometry and material properties of subsurface materials. Therefore, subsurface investigation was carried out through nine boreholes throughout the basin. Based on drill-logs, collected samples and laboratory test results, the subsurface soil profiles of nine areas in the basin are simplified for future strong ground motion simulation. Five subsurface layers in Tampuran, Krajan areas and six subsurface soil layers in Watu, Jl. Parangtritis, Wijirejo areas and seven layers in Jl. Parangtritis, Karang Semut, Bambang Lipuro areas and eight layers in Pranti area, have been simplified and the geotechnical properties of each layer have been evaluated as well. Keywords: Basin, Yogyakarta, depression, ground motion, earthquake.
ESTIMATION OF S-WAVE VELOCITY STRUCTURES IN YOGYAKARTA BASIN, INDONESIA Tun Naing; Subagyo Pramumijoyo; Hiroshi Kawase
Journal of Applied Geology Vol 1, No 2 (2009)
Publisher : Geological Engineering Department Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (2134.492 KB) | DOI: 10.22146/jag.7228

Abstract

For the theoretical simulation or prediction of strong ground motion, it is prime importance to get information of underground structures, especially for sedimentary layers overlying on bedrock, like in Yogyakarta Basin. The Standard Penetration Test, Spectral Analysis of Surface Wave (SASW) and other geotechnical properties are used to estimate S–wave velocity structures in this basin. SPT tests were conducted at nine sites and SASW measurements were performed at seventeen sites. As a result, the S-wave velocity structures of top 30 m depth had been evaluated in each site. The average shear wave velocity v30 s had been successful estimated and the sites are classified into three types; soft soil, medium dense soil and hard soil. All sites where SPT performed are on soft soil according to their v30 s . However, according to v30 s from SASW measurements, 10 sites are located on medium dense soils type, 5 sites on dense soils and 2 sites on soft soils. The acceptable equivalent S-wave velocitystructure is observed by comparing the results from SASW and geotechnical approach in Imogiri, Bambang Lipuro, Pundong (Watu, Pranti) and Pandak (Wijirejo) areas. Keywords: Ground motion, underground structure, sedimentary layer, SPT, SASW, Pundong
ESTIMATION OF MAXIMUM EARTHQUAKE MAGNITUDE OF EARTHQUAKE POTENTIALS FOR YOGYAKARTA DEPRESSION AREA, INDONESIA Myo Thant; Subagyo Pramumijoyo; Heru Hendrayana; Hiroshi Kawase; Agus Darmawan Adi
Journal of Applied Geology Vol 2, No 1 (2010)
Publisher : Geological Engineering Department Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (623.84 KB) | DOI: 10.22146/jag.7231

Abstract

Maximum magnitudes of earthquake potentials are estimated for Yogyakarta depression area by using the faultlength and earthquake magnitude relations for fault specific seismic sources. For estimation of maximum earthquake magnitude, the fault specific seismic sources are modeled as 18 normal faults and 6 strike-slip faults sources referring the geological map of McDonald, 1984 and Rihardjo et al., 1995. For the present area the subduction zone earthquakes are expected to happen in the offshore region regarding the study on the seismicity of the region and the focal mechanisms of the past earthquakes. So three area sources are also assumed for this region and the possible maximum earthquake magnitudes for these sources are determined by probabilistic approaches.
Evaluation of strong ground motion for Yogyakarta depression area, Indonesia Myo Thant; Subagyo Pramumijoyo; Heru Hendrayana; Hiroshi Kawase; Agus Darmawan Adi
Journal of Applied Geology Vol 2, No 2 (2010)
Publisher : Geological Engineering Department Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (2212.371 KB) | DOI: 10.22146/jag.7249

Abstract

The probabilistic seismic hazard maps are developed for Yogyakarta depression area. The earthquake catalog of ANSS (1970-2007) is taken into account with the complement of NEIC (USGS, 1973-2007) and the records of BMG (2000-2004). On the basis of seismicity of the area, tectonics and geological information, the seismic source zones are characterized for this area. The seismicity parameters of each seismic source are determined by applying the classical Gutenberg-Richter recurrence model, regarding the historical records. The attenuation relation for Yogyakarta depression area cannot be evaluated since the sufficient strong ground motion records are not available for this region. Therefore the attenuation relations which were developed for other territories as Europe and Japan are used for the present hazard calculation by validating, using the aftershocks records, modeling the peak ground acceleration maps for the recent event, 27 May, 2006, Yogyakarta earthquake inserting the damage area distribution pattern. The probabilistic seismic hazard maps are finally developed by using the McGuire (1976) EQRISK computer program by modifying for the present purpose. The seismic hazard maps expressed in term of peak ground acceleration are developed for the recurrence intervals of 10, 50, 100, 200 and 500 years