The back–arc thrust region in Eastern Java to Flores is significantly influenced by the arc–continent collision between the Australian Plate and the Eastern Sunda Arc, leading to a tectonic regime characterized by high seismic and volcanic hazards. This area has experienced several major earthquakes. However, back–arc thrust in Eastern Java remains absent from significant shallow earthquakes, which might indicate intense deformation. We conducted an analysis using recent and dense Global Navigation Satellite System (GNSS) observations from both continuous and campaign stations to develop a strain rate model and explore the detailed crustal behavior and strain accumulation within the Eastern Java back–arc thrust system. Our findings revealed varying values of compression and extension throughout the region, with compression values ranging from −2.24 to 0.086 μstrain/year. Additionally, we observed that the maximum shear strain rate and dilatation strain rate were within the ranges of 0.0013 to 1.12 μstrain/year and −2.24 to 0.698 μstrain/year, respectively. These findings could facilitate more informed strategies and improve preparedness for future seismic events.

Sempor Reservoir located in the Telomoyo River Basin in the Serayu River region is categorized as one of the priority watersheds based on the 2015-2019 Strategic Plan of the Ministry of Environment and Forestry. Priority watershed is a watershed that gets more attention in controlling water pollution, one of which is sedimentation. Watershed observation and management activities are needed for the reservoir to operate optimally. One of the observations and management activities of the Sempor Watershed is the calculation of sedimentation rate. In this research the sedimentation rate was calculated using the MUSLE method that included runoff parameter, erodibility, slope, land cover and conservation factor. The Sempor watershed boundary is obtained through delineation of DEM. The calculation is done by utilizing a Geographic Information System (GIS) through analysis of soil type maps, length and slope maps, land cover and conservation maps with the boundaries of the Sempor Reservoir. Based on this result, the Sempor Reservoir has a sedimentation rate of 166,173,500 tons/year and a sedimentation thickness rate of 3,7259 mm/year. According to the provisions of the Ministry of Forestry in 2009, the rate of sedimentation thickness in the Sempor Reservoir is included in the medium class. The river as one of the potential means of sediment transport contributes to the rate of sediment thickness of 3.7256 mm /year, while for areas outside the river coverage it only 0.003 mm/year. The river has a major influence on sedimentation in the Sempor Reservoir.

The Sermo Reservoir is located in Kulon Progo District, Special Region of Yogyakarta, Indonesia. It plays a vital role in providing water to its surrounding communities. According to the geological structure of this area, a fault exists near the Ngrancah River and passes through the reservoir’s inundation. At present, a network consists of 15 Global Navigation Satellite System (GNSS) monitoring stations spread around the Sermo Fault to monitor its deformation. However, this network was designed without consideration of geological parameters. This study aimed to design an optimal deformation monitoring network of the Sermo Fault by taking into account geological information and evaluate the existing network, specifically, the optimal distance for the station to the fault plane. Geological surveys were carried out to obtain information regarding the type and characteristics of the fault. This information was used as one of the parameters in the optimization design, using sensitivity criteria, of a network to monitor for the optimal distance between the observation station and fault. Using the strike-slip fault model, the optimal distance obtained was from 4.5 to 8.5 km from the fault plane. The existing stations of the Sermo Fault deformation monitoring network are about 0.07–3.3 km away from the fault. Therefore, the network is insufficiently sensitive and needs to be developed by adding stations that are more than 4.5 km away from the fault. This study designed an alternative network by rearranging the stations’ location to obtain a better configuration and sensitivity.

Sermo dam has operated for 20 years. This dam has a great benefit, especially as a water storage for water supply, irrigation and flood prevention. For the purposes of Sermo dam deformation monitoring, the control network was built around the Sermo dam in 2010. Then, this network was developed in 2015 by adding 5 new control points. For the time being, the network consists of 8 existing control points (micro) and 5 new control points (macro). The aim of the study is to monitor the control network displacement in the period of 2015 to 2016 based on GNSS observation data.GNSS measurement were conducted at 9 to10 of May 2015 and 12 to 15 of May 2016. The data observation was processed using GAMIT/GBLOK scientific software referenced to IGS station to determine the coordinates and its standard deviation. Further, horizontal and vertical displacement was analyzed by comparing with 2.5 times the standard deviation. The results showed that within a year, the coordinate difference varied from 0.12 to 1.68 cm on the N component, 0.21 to 0.65 cm on the E component, while the U component (the vertical displacement) have greater one, varied from 2.71 to 16.34 cm. Six control points (MAK2, MAK3, BMB2, BMB5, BMS2 and BMS5) have significant different in the horizontal displacement and six control points have significant different in vertical displacement (MAK5, BMB1, BMB2, BMS1, BMS2 and BMS3). In general, the horizontal displacement tends toward southeast. However, for obtaining more accurate and realistic results, further evaluation is required in the processing strategy such as the use of local control point as reference.

Letak Indonesia yang berada pada pertemuan empat lempeng yaitu Eurasia, Indo-Australia, Laut Filipina, dan Pasifik menyebabkan tingginya aktivitas tektonik termasuk terbentuknya sesar-sesar, salah satunya Sesar Baribis. Pergerakan sesar ini dapat diamati dengan pengamatan GNSS. Penelitian sebelumnya menggunakan data CORS untuk mengidentifikasi pola pergerakan Sesar Baribis. Penggunaan data stasiun CORS memiliki keunggulan yaitu data tersedia secara kontinu, namun CORS tidak dirancang khusus untuk memantau pergerakan sesar tersebut. Oleh karena itu perlu dilakukan evaluasi apakah stasiun CORS dapat mewakili pergerakan sesar tersebut. Penelitian ini menggunakan data tujuh stasiun CORS di sekitar Sesar Baribis pada tahun 2019 s.d. 2023 dan data campaign pengamatan GNSS di sekitar Sesar Baribis pada tahun 2019 s.d. 2021. Data tersebut diolah dengan metode Precise Point Positioning (PPP), kemudian dilakukan analisis laju dan arah pergeseran. Laju pergeseran dihitung dengan metode linear square adjustment. Evaluasi pergerakan CORS apakah dapat merepresentasikan pergerakan sesar atau tidak dilakukan dengan membandingkan pola kecepatan dan arahnya terhadap titik campaign yang memang didesain untuk pemantauan. Hasil penelitian menunjukkan bahwa titik pantau campaign secara keseluruhan memiliki laju pergeseran yang lebih besar dibandingkan dengan CORS. Sementara itu, arah pergeseran komponen horizontal titik CORS secara umum mengarah ke timur, sedangkan titik pantau campaign memiliki arah yang cukup beragam. Pola pergerakan stasiun CORS di sekitar Sesar Baribis tidak menunjukkan kesesuaian dengan tipe Sesar Baribis yaitu sesar naik, sekaligus tidak menunjukkan kesesuaian dengan pola laju dan arah pergeseran titik campaign. Dapat dikatakan bahwa stasiun CORS tidak merepresentasikan pola pergerakan Sesar Baribis.