3-D SEISMIC VELOCITY TOMOGRAPHY IN BALI AND NUSA TENGGARA REGIONS BY APPLYING FAST MARCHING METHOD USING BMKG SEIMOGRAPH NETWORK
Bali and Nusa Tenggara have high seismicity due to their location along the transition zone between the Indo-Australian subduction in the Sunda arc to the collision of the Australian continent in the Banda arc. Furthermore, there are the Flores Backarc Thrust and Wetar Thrust to the north of this...
Saved in:
| Main Author: | |
|---|---|
| Format: | Theses |
| Language: | Indonesia |
| Online Access: | https://digilib.itb.ac.id/gdl/view/69834 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| Institution: | Institut Teknologi Bandung |
| Language: | Indonesia |
| Summary: | Bali and Nusa Tenggara have high seismicity due to their location along the
transition zone between the Indo-Australian subduction in the Sunda arc to the
collision of the Australian continent in the Banda arc. Furthermore, there are the
Flores Backarc Thrust and Wetar Thrust to the north of this area, both of which
caused major earthquakes in the past, including the Flores earthquake and tsunami
in 1992 and the Lombok earthquake in 2018. The purpose of this study is to
determine the body wave velocity (Vp, Vs, and Vp/Vs ratio) beneath the Bali and
Nusa Tenggara regions. We used 4,587 earthquake data catalogs from the Agency
for Meteorology, Climatology, and Geophysics (BMKG) between 2019 and 2020 at
coordinates 1120 E – 1280 E and 40 S – 130 S. We obtained 50,857 P- and 16,797
S-wave phases by re-picking of 4,587 events from 90 BMKG stations. To determine
the hypocenter locations, we used the Non-Linear method, while the tomographic
inversion used the fast marching method through the FMTOMO program. The
results indicate several tectonic features in the study area, including the Indo-
Australian slab and Flores Backarc Thrust, which have high Vp anomalies, high Vs
anomalies, and low Vp/Vs ratio values. The angle of subduction of the Indo-
Australian plate in this area is between 100 and 300. Flores Backarc Thrust has
been identified by high Vp anomaly, high Vs anomaly, and low Vp/Vs ratio in the
northern part of Flores, which extends from the northern island of Flores to the
northern of Bali at a depth of about 4 km to 50 km. The east side of Sumba Island,
Savu Island, and Rote Island in the western part of Timor has high Vp, high Vs, and
low Vp/Vs ratios. Within the study area, volcanic zones exhibit low Vp, low Vs, and
high Vp/Vs ratios at a depth of 25 km. |
|---|