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Wilayah Lombok khususnya Kota Mataram dikategorikan sebagai kawasan dengan kerentanan tinggi terhadap gempabumi. Kota Mataram dikelilingi oleh beberapa zona sumber gempa termasuk subduksi dan back arc thrust. Peak Ground Acceleration (PGA) merupakan suatu parameter yang bisa menggambarkan dampak dari gempabumi. Pada penelitian ini kami menentukan persamaan terbaik untuk memperkirakan PGA di antara beberapa model yang ada. Metode yang digunakan untuk memilih persamaan adalah analisa residual dan Euclidean Disteance Ranking. Data yang digunakan terdiri atas nilai PGA dari accelerograph di Stasiun Geofisika Mataram (MAKE), katalog gempabumi di sekitar Mataram pada periode 2016 hingga 2018, dan kondisi situs di MAKE. Hasil penelitian menunjukkan bahwa beberapa persamaan memiliki hubungan yang baik dengan PGA hasil observasi di Kota Mataram yang penting untuk mitigasi gempabumi.

The western extension and deformation mechanism of Flores back-arc thrust in eastern Sunda-Banda Arc (Indonesia) are poorly investigated, and, thus, poorly constrained. From late July to August 2018, a sequence of large earthquakes (M6.4+) took place in the north of Lombok Island that marked the previously westernmost termination of the continuous zone of the back-arc thrusting. The 2018 Lombok earthquake sequences that began with Mw 6.4 (28 July 2018), and followed by Mw 6.9 (5 August 2018), and Mw 6.9 (19 August 2019) with massive subsequent aftershocks claimed on more than 500 casualties, nearly 500,000 people displaced and serious damages on Lombok Island. Here we relocate the aftershocks and perform the finite fault inversions of M6.4+ earthquake sequences constrained with teleseismic body and surface waves. Both refined hypocenters of aftershocks and rupture processes of large earthquakes provide detail kinematic descriptions of the source mechanisms of the sequences. The aftershocks distributions and slip model suggest that the earthquakes occurred on south-dipping low angle thrust faulting that striking to the east while it also activated aftershocks on surrounding complex shallow faulting with distinguishing distributions. The source inversions of large earthquakes over the entire of the western part of Flores back-arc thrust resulted as simple circular rupture propagations initiated from ~15 km depth for all events except the westernmost events (Mw 6.9 on 5 August 2019) that had a more complex rupture and initiated from shallower depth, and with slip distributed cross over the former identified westernmost termination of the Flores back-arc thrust. Our study suggests the further extension of back-arc thrusting and the possible structures revealed from the subsequence aftershocks. The source characterizations revealed in this study would be important for further seismic hazard analysis in this region.

Indonesia has a high level of seismic vulnerability because located in the junction area of four large plates, namely the Eurasian plate, Indo-Australian plate, Pacific plate, and Philippine Plate, and also the number of active faults that stretch throughout its regions. One of the efforts to mitigate earthquake disasters is to conduct seismic hazard microzonation efforts. The Research and Development Center of BMKG has carried out ongoing research in the field of seismic microzonation to obtain information on the level of seismic hazard in some regions based on microtremor parameter values, including in the Sukabumi (2009), Bantul (2010), Padang (2011), Cilacap (2012), Kulonprogo (2014), Tasikmalaya (2017), Garut (2018) and Pangandaran (2019). This study tries to prototype the seismic microzonation information system in a web-based spatial information system called InaSMIS (Indonesia Seismic Microzonation Information System). InaSIMS contains information about the analysis of microtremor survey results, including the value of the dominant period (T0), Ground Shear Strain (GSS), and USGS Vs30, which states the level of seismic hazard in an area. InaSMIS is still being developed in the research stage and is not yet an operational service for BMKG. In the future, InaSMIS expected to be a source of public information to determine seismic hazards in Indonesian regions.

Gempa bumi Banten berkekuatan 6,2 Mw pada tanggal 23 Januari 2018 menarik perhatian para ahli tentang pentingnya pengetahuan mengenai percepatan tanah maksimum dan spektra percepatan di permukaan untuk wilayah DKI Jakarta. Hasil PGA M , S MS , dan S M1 memegang peranan penting dalam peraturan desain seismik. wilayah DKI Jakarta. Hasil PGA M , S MS , dan S M1 memegang peranan penting dalam peraturan desain seismik. Tujuan dari penelitian ini adalah menentukan PGA M , S MS , dan S M1 untuk wilayah DKI Jakarta menggunakan Probabilistic Seismic Hazard Analysis (PSHA). Data yang digunakan adalah katalog gempa bumi BMKG, ISC, dan USGS dari tahun 1900 – 2018. Hasil analisis menunjukkan bahwa nilai PGA M untuk untuk probabilitas terlampaui 2% dalam 50 tahun di wilayah DKI Jakarta bervariasi dari 0,35 – 0,5 g. Sementara itu nilai S MS , dan S M1 untuk untuk probabilitas terlampaui 2% dalam 50 tahun di wilayah DKI Jakarta bervariasi dari 0,65 – 1g dan 0,8 – 1g. Nilai PGA M , S MS , dan S M1 relatif lebih tinggi di wilayah Kota Jakarta Selatan, Kota Jakarta Barat, dan Kota Jakarta Utara. The Mw 6.2 Banten earthquake on January 23, 2018, draws researchers’ attention to the importance of information about Peak Ground Acceleration and spectral acceleration on the surface for the DKI Jakarta area. The results of PGA M , S MS , and S M1 play an important role in the rules of seismic design. The purpose of this study was to determine PGA M , S MS , and S M1 for the DKI Jakarta area using Probabilistic Seismic Hazard Analysis (PSHA). The data used are the earthquake catalog BMKG, ISC, and USGS from 1900 - 2018. The analysis shows that the value of PGA M for DKI Jakarta varies from 0.35 – 0.5 g. Meanwhile, the value of S MS , and S M1 varies from 0.50 - 0.1 g and 0.8 - 1 g. The values of PGA M , S MS , and S M1 are relatively higher in the area of South Jakarta City, West Jakarta City, and North Jakarta City.

Relokasi hiposenter gempabumi penting dilakukan untuk mendapatkan lokasi gempabumi dengan ketelitian yang tinggi, analisa pola tektonik, studi model struktur kecepatan, dan analisis seismisitas untuk studi global maupun studi lokal. Metode relokasi yang digunakan adalah metode teleseismic Double-Difference yang menggunakan model kecepatan seismik 3D. Penelitian ini dilakukan dengan merelokasi gempabumi yang terjadi di sekitar wilayah Laut Maluku. Jumlah gempabumi yang direlokasi adalah sebanyak 7042 dari 8845 gempabumi. Hasil dari relokasi hiposenter menggunakan teleseismic Double-Difference menunjukkan hiposenter yang lebih baik, yaitu gempabumi dengan kedalaman tertentu (fixed depth = 10 km) telah terelokasi dan distribusi hiposenter yang didapat menunjukkan pola penunjaman yang berasosiasi dengan zona subduksi di wilayah Laut Maluku. Earthquake relocation is important to be applied for obtaining high resolution of earthquake location, analyzing tectonic setting, studying velocity structure model, and anlyzing global and local studies of seismicity. One of the relocation methods was teleseismic Double-Difference method which use 3D seismic velocity model. This research has been conducted by relocating the earthquake that occurred in the Mollucas Sea. We relocated 7042 of the 8845 earthquakes. Results of the hypocenter relocation using teleseismic Double-Difference show a better hypocenter, so earthquakes with a certain depth (fixed depth = 10km) has been relocated and the distribution of hypocenter relocation may indicate the tectonic phenomenon such as subduction in Mollucas Sea.

Gempa bumi tektonik 23 Januari 2018 berkekuatan M 6,1 telah mengguncang wilayah Lebak dan sekitarnya. Guncangan gempa bumi ini berdampak berrisiko yang cukup serius. Menjadi perhatian dari peristiwa ini adalah pusat gempa bumnyai berada di laut pada zona sesar Cimandiri sebagai kelanjutan dari zona sesar yang berada di daratan. Penelitian ini berhasil melakukan relokasi episenter dan hiposenter gempa bumi bersumber dari BMKG dari tanggal 23 hingga 28 Januari 2018 sebanyak 62 kejadian gempa bumi, menentukan bidang sesarnya, dan perkiraan transfer tekanan Coulomb gempa bumi utama (mainshock). Relokasi hiposentrum gempa bumi menunjukan adanya lineasi sumber gempa bumi yang mengarah baratdaya-timurlaut dan berasosiasi dengan terusan zona sesar Cimandiri ke arah arah daratan di Teluk Pelabuhan Ratu. Pengolahan HC-plot dapat menentukan bidang sesar sebenarnya pada gempa bumi Lebak yaitu bidang nodal 2 dengan nilai jurus N 41.79° E, kemiringan 81.4°, rake 43.9°. Selain itu analisis perubahan nilai tekanan Coulomb gempa bumi menunjukkan pengaruh gempa bumi utama yang menyebabkan terjadinya gempa bumi susulan di sekitar wilayah sumber.

Earthquake magnitude M 5,6 shaken around Deli Serdang, North Sumatera on January 16th 2017. This research aims to understand Coloumb stress changes of Deli Serdang Earthquake. The analysis of Coloumb stress changes has done to indicate the influence of mainshock toward aftershocks. Earthquake source mechanisms data obtained from Global Centroid Moment Tensor (GCMT) and German Research Centre for Geosciences (GFZ). The distribution of the mainshock and aftershocks had been relocated using Modified Joint Hypocenter Determination (MJHD) method. We used arrival time of primary and secondary wave phase to relocate the hypocenter. The data obtained from the Indonesian Agency for Meteorology Climatology and Geophysics (BMKG) in the period from January 16th 2017 to January 30th 2017. Keywords: Coloumb stress changes, MJHD relocation, Deli Serdang earthquake

Earthquake hypocenter relocation is need to be done to get a better earthquake location with high accuracy so tectonic setting, and seismicity analysis can be get and done for further studies. One of some method to relocate earthquake is teleseismic Double-Difference that used 3D velocity model. This research is done by relocating 7042 of 8845 available earthquakes from January 1st 2009 – June 12th 2016 in Moluccas Sea. The result are better earthquake depths, showed by no more fixed depth earthquakes and hypocenter distribution shows subduction pattern which is assossiated to Moluccas Sea Plate. Subducting Plate of Moluccas Sea below Sangihe is getting deeper more way it gets north (± 580 km) and sloping to the south (± 280 km) and the subducting Moluccas Sea below Halmahera Arc is 250 km depth on average. Another result is a rollback of Phillipine plate is found that moves along with Moluccas Sea plate which is subducting below Halmahera Arc.

Bali dan Nusa Tenggara memiliki kondisi tektonik yang komplek. Aktivitas seismik umumnya pada wilayah penelitian berasal dari subduksi lempeng Indo-Australia (Busur Sunda), patahan naik busur belakang, dan juga aktivitas vulkanis. Penelitian dilakukan untuk mengetahui seismisitas, pola tektonik dan menghitung sudut penujaman lempeng di wilayah Bali hingga Nusa Tenggara berdasarkan metode relokasi Teleseismic Double-Differencedengan model kecepatan 3D. Data yang digunakan adalah data katalog gempabumi BMKG pada periode pengamatan Januari 2010 – Februari 2017 sebanyak 4201 kejadian gempabumi. Hasil relokasi menunjukkan pola sebaran gempabumi yang didominasi oleh gempa-gempa dangkal di wilayah barat daerah penelitian, dan semakin ke arah timur semakin dalam, yang mengindikasikan bahwa gempa tersebut berasal dari zona subduksi