MEKANISME GERAKAN MASSA BATUAN AKIBAT GEMPABUMI; TINJAUAN DAN ANALISIS GEOLOGI TEKNIK
ABSTRACT: More than
150 events of
rock mass movement
(rock slides and
rock falls) were
recorded at the
west and north parts
of Southern Mountain,
as the impact
of earthquake last
May 27, 2006
in Daerah Istimewa
Yogyakarta. The susceptible areas
for those rockslides and
rockfalls were formed
by steep volcanic
rocks such as
interbeded tuff sandstone – tuff
claystone, andesitic breccia
and limestone. One
major fault with
the direction of
NE-SW with several corresponding micro faults were
apparent to be the significant control on the stability of rock mass, which
then lead to the movement through
mechanism of rock
falls and rock
slides. One of
the largest event
occurred at the
slope of tuffaceous sandstone
situated in Desa Sengir, Kecamatan Prambanan where 2 hectars of land moved and
resulted in 16 houses damaged. Interpretation of
detailed aerial photograph
( 1 :
5,000) and geological
site investigation by
drilling through three bore holes with the total depth of 46 m were
carried out to preliminary investigate the mechanism of rock mass movements
and the major
controlling factors. The
movement of rock
mass in Sengir
occurred as the
wedge rock sliding through the
intersection of two joint sets (N 100 o E
and N 175 o E) and the bedding
dip of tufaceous sandstone – mudstone
with the direction
of N 210oE/
10o. The major
controls of this
rock sliding were
rock joint existence
and orientation, the direction
of bedding plane
at the slope
and the difference
of rock weathering
grade. Those major controlling factors
are important to be considered
for establishment of
landslide susceptibility map
at the surrounding area.
Keywords: rock mass movements, earthquake, controlling
factors, establishment of landslide
Penulis: Dwikorita Karnawati
Kode Jurnal: jptsipildd070019
