Estimation of Slip Distribution of the 2007 Bengkulu Earthquake from GPS Observations Using the LeastSquares Inversion Method

Continuous  Global  Positioning  System  (GPS)  observations  showed significant  crustal  displacements  as  a  result  of  the  Bengkulu  earthquake occurring on September 12, 2007. A maximum horizontal displacement of 2.11 m was observed at PRKB station, while the vertical component at BSAT station was lifted up with a maximum of 0.73 m, and the vertical component at LAIS station had subsided  "“0.97 m. Adding more constraints on the inversion for the Bengkulu earthquake slip distribution inferred from GPS observations can help solve  the  underdetermined  least-squares  inversion.  Checkerboard  tests  were performed  to  help  conduct  the  weighting  for  constraining  the  inversion.  The inversion calculation yielded an optimal value for the slip distribution by giving the smoothing constraint a weight of 0.001 and the slip constraint a weight of = 0 at the edge of the earthquake rupture area. The maximum co-seismic slip of the optimal inversion calculation was 5.12 m at the lower area of PRKB station and BSAT station. The seismic moment calculated from the optimal slip distribution was 7.14 x 1021 Nm, which is equivalent to a magnitude of 8.5

TECTONIC STRAIN AND SEISMIC HAZARD ESTIMATION IN SUNDA STRAIT BASED ON GPS OBSERVATION DATA

Sunda strait has a relatively high seismic activity. The high seismic activity was caused by the seismic zoneat that region, including the faults zone. Based on the high seismic activity in the Sunda Strait, it is necessary to doresearch about the strain that occurred in the Sunda Strait region to determine the tectonic activity in that area andits seismic hazard. To observe the tectonic activity in the Sunda Strait, GPS observations were made periodicallywith static differential method at the observation points located in the Sunda Strait region. Based on the strainanalysis, the southwestern part of the Sunda Strait tend to experience compression and the northeastern part tendto experience extention. Sunda Strait had a relatively high seismic hazard with maximum PGA 0,47 g

Quality control in GNSS reflectometry method for tide observations

Recently, the reflected signals from global navigation satellite systems (GNSS) have been utilized to observe coastal tides, and it has been found that this method provides promising results. Although this method is promising, there remain problems related to accuracy of the observed tides. The purpose of this study was to improve the accuracy by employing an optimal spectral method in the quality control scheme. The quality control process is carried out by setting parameters to achieve the best possible frequency correlated with sea levels such as estimation of the noise frequency range, frequency amplitude power selection, and selection of peak frequency to noise ratio. The results using the data at Morotai station showed that the amplitude power less than 5 comes from low-frequency signals and hence it is an indicator that the Lomb-Scargle periodogram (LSP) fails to determine the dominant frequency. In addition, the result of the peak frequency to noise ratio shows a value of 2.7, meaning that the peak frequency of the LSP signal is at least 2.7 times greater than the signal noise. Quality control sensitivity settings are very effective in determining the reflectors height coming from the sea level. The periodogram visualization can be used to decide which LSP is significant

PEMODELAN SUMBER TEKANAN GUNUNG SINABUNG MENGGUNAKAN SKEMA INVERSI PARTICLE SWARM OPTIMIZATION (PSO)

Gunung Sinabung merupakan salah satu gunung aktif diindonesia yang masuk dalam gunungapi tipe A setelah erupsi pertama kali pada tahun 2010 setelah sebelumnya tidak ada aktivitas erupsi. Gunung sinabung terus erupsi hingga saat ini yang mejadikan Gunung Sinabung perlu diamati lebih lanjut terkait aktivitas yang terjadi serta dilakukan pemodelan untuk memprediksi kondisi bawah permukaan yang dapat membantu proses analisis. Pemodelan terhadap data permukaan Gunung Sinabung yang berasal dari data pergeseran permukaan dari GPS pada tahun 2015-2016 telah dimodelkan dengan skema inversi particle swarn optimization (PSO). Erupsi yang terus menerus pada tahun tersbut menghasilkan data yang sangat fluktuatif dengan hasil inversi menunjukan bahwa sumber tekanan pada tekanan pada Gunung Sinabung terletak pada kedalaman dangkal yaitu 0,5km hingga 1,0 km dibawah permukaan laut dibawah Gunung Sinabung, dengan sumber tekanan yang dangkal serta adanya inflasi pada tubuh gunung api maka memungkinkan adanya erupsi secara kontiyu dalam waktu yang singka

Akumulasi Regangan di Sumatera Berdasarkan Data Pengamatan GPS Tahun 2002-2008 dan Dampak Kerusakan Lingkungan Akibat Pelepasan Regangan

Pulau Sumatera terletak di antara dua lempeng tektonik yaitu lempeng Indo-Australia dan lempeng Eurasia. Intensitas gempa bumi sangat besar di pulau ini, terutama di sepanjang daerah pesisir barat. Pada 2002-2008 periode, banyak gempa bumi besar yang menyebabkan korban jiwa dan kerusakan lingkungan. Fenomena ini menunjukkan bahwa studi tentang pola deformasi pulau Sumatera sangat diperlukan. Studi yang diperlukan adalah untuk rencana mitigasi bencana di masa depan. Pola deformasi gempa dapat diamati dengan GPS pengamatan (Global Positioning System). Data yang digunakan untuk gempa Sumatera adalah GPS Sumatera Array (SuGAr). Perangkat lunak yang digunakan untuk data Array GPS Sumatera dari pulau Sumatera adalah Gamit 10.4. Dari hasil pengolahan data, dapat disimpulkan bahwa data perpindahan koordinat stasiun dapat digunakan jika data outlier telah terhapus. Dari koordinat perpindahan stasiun bisa diperoleh vektor perpindahan semua stasiun sebelum, selama atau setelah gempa bumi. Dari perpindahan nilai-nilai vektor, nilai regangan yang terjadi di sepanjang pulau Sumatera dapat diperkirakan. Dari data regangan, nilai akumulasi regangan 2002-2008 dapat diperoleh. Sehingga dapat dianalisis wilayah yang berpotensi terjadinya gempa selanjutnya

The Potential of the Land Value Capture Scheme in the Perspective of Disaster Risk Funding

Disaster risk refers to the possibility of a loss of life, assets, health, and livelihoods to the community in the future, so it must be reduced, one of which is by implementing disaster risk management. The disaster risk management financing scheme is crucial considering the number of funds needed. This research serves as an initial exploration into alternative funding options by investigating the potential benefits of implementing the Land Value Capture (LVC) scheme. The driving question of this study focuses on the advantages of employing the land value capture concept for disaster risk funding. To address this question, a descriptive qualitative research methodology is employed, encompassing an analysis of LVC in general, a funding analysis for disaster risk management, and the implementation of LVC for disaster risk reduction specifically in Indonesia. The findings of this study reveal that the Land Value Capture (LVC) scheme can serve as an additional strategy for funding disaster risk management in Indonesia. Through the proposed framework, the integration of LVC with disaster risk financing and insurance is facilitated

The Mechanisms of Coastal Erosion in Northeast Bali

Marine tourism sector in the Northeast Bali, Indonesia, experienced rapid development in the last decades. However, severe coastal erosion in some parts of the area has threaten the industry. Unsuccessful mitigation measures have been carried out by authorities by constructing seawalls along the coastline. The objective of the study is to understand the physical processes related to coastal erosion in the area and to assess the effectiveness of seawall along the coastline. To achieve the objectives, a GIS approach was carried out to investigate general changes of the coastline since 1944 until 2013. Hydrodynamics analyses and sediment transport simulations were also conducted and validated by the data from field measurements. The role of Mount Agung (a volcanic mountain) to the coastal dynamic system was also investigated. Moreover, the data from cGPS measurements in the island were also used for the analysis of possible land subsidence in the area. From social aspects, the history of USAT Liberty Shipwreck in Tulamben Village supports the analyses and provides information on the evolution of coastline in the area. We conclude that coastal erosion in North-east Bali has long been occurred and strongly affected by the dynamics of hydro-oceanography, volcanic activities, geological dynamics, and human interferences. Finally, the mechanism of coastal erosion in the area was also proposed