p–ISSN: 2723 - 6609 e-ISSN: 2745-5254
Vol. 5, No. 6 June 2024 http://jist.publikasiindonesia.id/
Jurnal Indonesia Sosial Teknologi, Vol. 5, No. 6, June 2024 2971
Lembang Fault Deformation Study Using Sentinel-1A Image
with PS-Insar Method
Rian Nurtyawan
1*
, Rizky Berzata Sigiro
2
Universitas Pakuan Bogor, Indonesia
1
, Institut Teknologi Nasional Bandung, Indonesia
2
*Correspondence
ABSTRACT
Keywords: Deformation;
PS-InSAR; Lembang
Fault.
The National Disaster Management Agency (BNPB) stated
that the number of earthquakes that occurred in Indonesian
territory during 2018 was 11,418. Nearly 95 percent of
earthquakes occur in fault areas and plate boundaries. The
methodology of this study has four main stages of data
processing, namely the differential interferogram stack stage
and coregistered stack formation using SNAP software. The
results of the study concluded that the average deformation
along the Lembang Fault was 2,485 mm, with a graph that
tended to rise. The area most affected by deformation is
Cisarua District, with a Line-of-Sight deformation speed of
28.4 – 48.9 mm/year. The most minor deformation occurred
in Lembang Regency with a Line-of-Sight deformation
speed of -2.3 – 19.2 mm/year. Conclusion The PS-InSAR
method has proven to be effective in mapping the speed of
Line-Of-Sight (LOS) deformation along the fault path. PS-
InSAR data shows that deformation in the Lembang Fault
ranges from an average of 2,485 mm, with an increasing
trend from January 2018 to March 2019. The area most often
affected by deformation is Cisarua District, West Bandung
Regency, with the LOS deformation rate reaching 28.4 to
48.9 mm per year.
Introduction
The Lembang Fault is one of the faults that is estimated to be an active fault that
will trigger earthquakes in West Java, especially in the Bandung area (Aji, Prasetyo, &
Awaluddin, 2018). The Lembang fault depicts the topography as a gawir that extends
west-east and is located north of Bandung City in West Java (Y Prasetyo & Firdaus,
2019). This fault is a canal from the northern end of the Cimandiri fault (PSGN, 2017).
The activity level of the Lembang Fault is not well known, so more integrated research is
needed from several methods, including seismic methods, gravity methods, and
deformation methods (Rasmid, 2014).
Deformation can be an essential parameter to determine the presence and impact of
an earthquake (Arintalofa, Yulianto, & Harmoko, 2020). Deformation is a change in
position, absolute or relative movement of the position of a material, or a change in
Rian Nurtyawan, Rizky Berzata Sigiro
Jurnal Indonesia Sosial Teknologi, Vol. 5, No. 6, June 2024 2972
position in linear dimensions (Andreas, 2001 in Jamel, 2013). The amount of deformation
can be analyzed through SAR image data using the InSAR, DinSAR, and PS-InSAR
methods (Yudo Prasetyo & Subiyanto, 2014). The PS-InSAR technique is a development
of conventional techniques InSAR and DInSAR (Lesniak, 2008). The main principle of
the PS-InSAR technique is utilizing multitemporal SAR image observation data over long
time spans to detect potential points of coherence. These points are then analyzed over
some time to see their displacement (Maghsoudi, van der Meer, Hecker, Perissin, &
Saepuloh, 2018).
Sentinel-1A satellite imagery is imagery produced by the Sentinel-1A satellite
designed and developed by the European Space Agency (ESA) in 2014. Citra Sentinel 1
has three product types, consisting of SLC (Single Look Complex), GRD (Ground Range
Detected), and OCN (Level-2 Ocean) (RoseGIS, 2018). SLC products consist of focused
radar data, geo-referenced using orbit and altitude data from satellites, and are available
on slant-range geometry (Syahputri, Anjasmara, & Hayati, 2023). Sentinel-1A can
observe the Earth's surface during the day and night with a repeat cycle every 12 days.
There are four acquisition modes owned by Sentinel-1A, namely Stripmap (SM),
Interferometric Wide Swath (IW), Extra Wide Swath (EW), and Wave (WV). IW is the
main recording that focuses on land where the recording area is 250 km2 and has a spatial
resolution of 5 m to 20 m (single look).
Method
This research methodology has four main stages of data processing, namely the
differential interferogram stack and coregistered stack formation stages using SNAP
software, StaMPS processing to analyze the selection and calculation of PS point
deformation using Matlab software, spatial subsetting stage or limiting deformation
results according to the Lembang Fault path using RStudio software, layouts using QGIS
software, and calculating the average LOS deformation using Microsoft Excel software.
The research methodology can be seen in Figure 1. The study began by forming eight
images into differential interferograms and coregistrated stacks. These two stacks are
each exported using the StaMPS export operator in the SNAP software in the form of a
folder structure required by the StaMPS program and then used the mt_prep_snap
command on the Ubuntu terminal to calculate the stability of the amplitude by entering
the dispersion threshold of 0.4. Furthermore, the Matlab software uses StaMPS scripts to
identify Permanent Scatterers (PS) and estimate deformation. After obtaining the results
as a time series Line-Of-Sight velocity of deformation, extraction is carried out as a CSV
table to limit or spatial subset according to the Lembang Fault path area. The PS points
are then laid out using QGIS software, which produces a map depicting the deformation
of the Lembang Fault.
Lembang Fault Deformation Study Using Sentinel-1A Image with PS-Insar Method
Jurnal Indonesia Sosial Teknologi, Vol. 5, No. 6, Juny 2024 2973
Figure 1
Research Methodology
Results and Discussion
The Lembang Fault deformation study results in the form of the LOS Velocity of
Deformation Map in time series (mm/year) from 2018 to 2019. The velocity of the
deformation value can be harmful, which means that the study area is down, or it can be
positive, which means the research area is up (Rohmah, 2017). These results can be seen
in Figure 2. According to the results of the study, it can be explained that the Lembang
Fault experiences LOS velocity of deformation represented by color points, ranging from
the smallest value of -2.3 mm/year marked with yellow color to the most significant value
with purple color, which is 48.9 mm/year. The research area along ± 29 km processed
from observations from January 2018 to March 2019 produced 15,542 PS points and
obtained an average deformation LOS value of 2,485 mm (Muvid, 2018).
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Jurnal Indonesia Sosial Teknologi, Vol. 5, No. 6, June 2024 2974
Figure 2. Lembang Fault Deformation Map
Deformation Trend Analysis
Based on the study's process and results, the Lembang Fault experiences
deformation that varies uplift and subsidence. The resulting deformation values are
positive and negative. The average value of LOS deformation can be summarized in one
graph. The graph, as shown in Figure 3, illustrates the deformation trend in the Lembang
Fault from January 2018 to March 2019.
In the future, the number of generations will move according to the human life
cycle; of course, the existence of technology will be beneficial and more accessible. The
results and discussions in the multi-finance industry, which is divided into three asset
categories, have their challenges, where those included in the 10 T > assets will maintain
and, if possible, will move to become leaders. Likewise, for multifinance companies with
assets of 5-10 T and 1 -5 T, whether they decide to be aggressive or survive. For
companies that are still in the asset category between 5 -10 T and 1 - 5 T, of course, they
will expect to be able to have a more significant amount of assets, which will undoubtedly
be attractive to investors who will invest their funds which have an impact on the low
cost of funds so that the segment of financed debtors will be lower risk so that the portion
of technology spending can be increased.
Lembang Fault Deformation Study Using Sentinel-1A Image with PS-Insar Method
Jurnal Indonesia Sosial Teknologi, Vol. 5, No. 6, Juny 2024 2975
The initial mapping of organizational conditions, especially for IT and Digital
departments or directorates, will make it easier for a company to determine organizational
goals in the next 3-5 years. The latest opportunities and innovations will always emerge;
by using PASTEL analysis SWOT in the use of technology through website media in the
multifinance industry, every multifinance company has an overview of a company's
strategy in information technology and digitalization. By also paying attention to the
opportunities and threats of each category of asset-based finance companies, you can see
how a company applies technology in supporting business and the process of adapting to
technology and digitalization by using applications such as digital signatures, third-party
data to see the credit history of prospective debtors.
Figure 3. LOS Tren Deformation
In January 2018, the average deformation LOS was -4,703 mm. It decreased in
March 2018 to -9,133 mm and rose sequentially from May 2018 to March 2019 with a
value of -5,381 mm, 3,309 mm, 5,559 mm, 13,230 mm, and 14,513 mm. Overall, the
deformation trend in the Lembang Fault tended to rise or uplift from January 2018 to
March 2019. However, there was also a decrease or subsidence in March 2018.
Largest Deformation Analysis
The largest categorized LOS Velocity of Deformation value is 28.4 and 48.9
mm/year. After analysis per sub-district, it can be concluded that the most considerable
deformation on the Lembang Fault occurred in the Cisarua District, West Bandung
Regency. The area consists mainly of settlements, which shows that the risk of
deformation impact on the Cisarua District is higher. The results of this analysis can be
seen in Figure 4.
-15,000
-10,000
-5,000
0,000
5,000
10,000
15,000
20,000
03/01/2018 04/03/2018 03/05/2018 02/07/2018 11/11/2018 10/01/2019 11/03/2019
Deformasi (mm)
Waktu (dd/mm/yyyy)
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Jurnal Indonesia Sosial Teknologi, Vol. 5, No. 6, June 2024 2976
Figure 4. The Largest Deformation of the Lembang Fault
Smallest Deformation Analysis
In addition, the most minor deformation in the study area was also analyzed. The
smallest category is the one that is valued between -2.3 to 18.2 mm/year. Areas with such
values are located in Lembang District, West Bandung Regency. According to the results
of this study, it can be concluded that this area has the lowest risk of deformation impact
and is relatively safe (Awaliah, 2020). However, that does not mean this region does not
need preventive measures. This is because the community settlement is very dense and is
precisely on the main fault line. The results of this minor deformation analysis can be
seen in Figure 5.
Lembang Fault Deformation Study Using Sentinel-1A Image with PS-Insar Method
Jurnal Indonesia Sosial Teknologi, Vol. 5, No. 6, Juny 2024 2977
Figure 5. The most minor deformation of the Lembang fault
Analysis of minor faults
The Lembang Fault is a major fault that stretches along 29 km. In addition to
significant faults, minor fault structures are of concern in this study. These minor faults
are located in the south and north of the main fault. Many community settlements above
it occupy this fault. Therefore, it is also necessary to analyze the existence of this
settlement because settlements on the main fault line need to be considered for mitigation
actions, as well as settlements on minor faults. As a sample, we can see the appearance
of minor faults quite widely occupied by settlements in Figure 6.
Gambar 6. Pemukiman pada Sesar Minor
Deformation Percentage Analysis in Settlements
Based on the data processing results using the PS-InSAR method, as many as
15,542 PS points were obtained for deformation points. Then, these points were overlaid
with residential areas. The results showed 10,249 PS points, or 66%, in settlements. This
shows that most of the settlement activity on the Lembang Fault caused deformation, both
in the direction of uplift and subsidence. Furthermore, analysis was carried out in each
sub-district on the Lembang Fault to see where the density of the deformation point was
greatest. After the sub-district boundaries are plotted, as shown in Figure 7, it can be
analyzed that the percentage of settlements affected by deformation is highest in Cisarua
District, West Bandung Regency.
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Jurnal Indonesia Sosial Teknologi, Vol. 5, No. 6, June 2024 2978
Figure 7. Percentage of Settlements Affected by Deformation
Conclusion
Based on the results of the study on the Lembang Fault, the PS-InSAR method has
proven to be effective in mapping the speed of Line-Of-Sight (LOS) deformation along
the fault path. PS-InSAR data shows that deformation in the Lembang Fault ranges from
an average of 2,485 mm, with an increasing trend from January 2018 to March 2019. The
area most often affected by deformation is Cisarua District, West Bandung Regency, with
the LOS deformation rate reaching 28.4 to 48.9 mm per year. This information is
important as an early warning for earthquake disaster mitigation in the region.
Meanwhile, Lembang District, also in West Bandung Regency, experienced a more minor
deformation with LOS speeds ranging from -2.3 to 19.2 mm per year. However,
settlements in Lembang District are still at risk because they are located in the Lembang
Fault Line area.
Lembang Fault Deformation Study Using Sentinel-1A Image with PS-Insar Method
Jurnal Indonesia Sosial Teknologi, Vol. 5, No. 6, Juny 2024 2979
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