SEDIMENT LAYER AND ENGINEERING BEDROCK ESTIMATION USING HVSR METHOD FOR SEISMIC HAZARD ANALYSIS AT SEMARANG CITY, CENTRAL JAVA
Semarang, Central Java has seismic hazard potentials because of the existence of active faults such as semarang fault, ungaran 1 fault, and ungaran 2 fault. Based on geological conditions, this region consists of alluvium sediment, sedimentary rocks, and volcano deposits which could cause amplifi...
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| Format: | Theses |
| Language: | Indonesia |
| Online Access: | https://digilib.itb.ac.id/gdl/view/63795 |
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| Institution: | Institut Teknologi Bandung |
| Language: | Indonesia |
| Summary: | Semarang, Central Java has seismic hazard potentials because of the existence of
active faults such as semarang fault, ungaran 1 fault, and ungaran 2 fault. Based
on geological conditions, this region consists of alluvium sediment, sedimentary
rocks, and volcano deposits which could cause amplification when earthquakes
occur. Dominant period, depth of sediment and engineering bedrock, and also
surface PGA estimation is a mitigation effort to understand seismic hazard which
was done in this research. The data used in this research is microtremor data that
has been acquired by Meteorological, Climatological, and Geophysical Agency
(BMKG). The writer's applied HVSR method using HVSRPY software to get the
dominant period that is reciprocal of dominant frequency. The dominant period in
Semarang city is obtained in the range 0.12-2.0s. Depth of sediment profile and
engineering bedrock is obtained from H/V curve inversion that has been done in
DINVER software. Depth of sediment with Vs value 500 m/s is obtained in the
range 50-300 m. Depth of engineering bedrock with Vs value 750 m/s is obtained
in the range 50-450 m. Surface PGA is obtained from calculation between
bedrock PGA with site coefficient based on Vs30 classification. Surface PGA in
Semarang city is obtained in the range 0,3-0,8 g. The scatter of dominant period
and depth of engineering bedrock has the same pattern in the north and east that
has greater value than in the south and west area in Semarang city. Pattern of
surface PGA in Semarang city has greatest value in the south then gradually
decreases to the north. So based on surface PGA, the south area of Semarang city
relatively has greater seismic hazard than in the north. Nevertheless, the north
and east area of Semarang city has a great dominant period and engineering
bedrock has relatively high amplification potential in Semarang city |
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