ABSTRACT
In response to the last May 27, 2006 of Bantul Earthquake with the magnitude of 5.9 Richter Scale,
more than 5000 people died and about hundred thousands of houses in Bantul, Sleman and Gunung
Kidul Regencies were damaged or collapced. To support the recovery and reconstruction of those
damaged areas it is urgent to provide a microzonation of earthquake hazard map which can
estimate the zonation of earthquake susceptibility at various level of risk.
Interpretation on the aerial photographs and satelite images, reviews on previous geological study
at Yogyakarta Basin and the surrounding areas, and site investigations by drilling, well logging,
geophysical surveys (georadar, magneto tuleric and resistivity surveys) as well as micro tremor
survey was conducted to establish the hazard map, especially at the area surrounding Opak – Oya
rivers.
Results of this investigation confirmed that the local ground conditions such as distribution and
density of loose sediments, distribution of faults, as well as the depth and distribution of
groundwater table dictated the severity of construction damages. In addition, some soil mechanic
analyses was also conducted to support the enhancement of Building Code in the earthquake
vulnerable area.
By
Dwikorita Karnawati
Geological Engineering Department, Gadjah Mada University, Yogyakarta, Indonesia, 55281,
email: dwiko@indosat.net.id
Salahuddin Husein
Geological Engineering Department, Gadjah Mada University, Yogyakarta, Indonesia, 55281,
email: shddin@gmail.com
Subagyo Pramumijoyo
Geological Engineering Department, Gadjah Mada University, Yogyakarta, Indonesia, 55281,
email: bagyo@ugm.ac.id
Antonius Ratdomopurbo
BPPTK, Volcanic Survey of Indonesia in Yogyakarta (was), Geological Survey Centre (present), Jl.
Diponegoro 57, Bandung, Indonesia, 40122
Koichiro Watanabe
Department of Earth Resources Engineering, Faculty of Engineering, Kyushu University, Fukuoka
819-0395, Japan, email: wat@mine.kyushu-u.ac.jp
Robert Anderson
California Seismic Safety Commission, 1755 Creekside Oaks Drive, Suite 100, Sacramento,
California, USA, 95833, email: anderson@stateseismic.com
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