Imanuela Indah Pertiwi
BMKG Balai Besar Wilayah IV Makassar

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Journal : Jurnal Geosaintek

Identifikasi Kualitas Site Seismik di Sulawesi Tenggara Berdasarkan Analisis Spektrum Noise Seismik Trismahargyono, Trismahargyono; Pertiwi, Imanuela Indah
Jurnal Geosaintek Vol. 9 No. 1 (2023)
Publisher : Institut Teknologi Sepuluh Nopember

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Abstract

Seismic stations are usually located in bedrock areas and stored in boreholes with the aim of protecting the seismometer from temperature and vibration due to weather changes. In general, the most widely used seismometers are broadband seismometers which have a wide frequency range so they record a lot of noise. PSD and PDF analysis were used to evaluate the noise characteristics of seismic stations. The standardization of high and low seismic noise refers to the Peterson Model. This research was conducted with the aim of knowing the quality of seismic stations in Southeast Sulawesi through analysis of the level of seismic noise sources that affect the quality of seismic data. The evaluation of the seismic site quality is based on the PSD value percentage parameter by calculating the PSD value of the signal recorded on June 17 to June 20, 2022. Various kinds of seismic noise in the resulting spectrum will be seen whether it is still within the limits of the Peterson Model or not. Based on the signal spectrum images obtained, there are 9 seismic sites in Southeast Sulawesi with ideal site quality, which can record seismic signal data and seismic noise sources activity well, namely BBSI, KKSI, PKCI, RKCM, WKCM, UKCM, WWCI, and KDI. Meanwhile, one seismic site with poor site quality cannot record seismic signal data and seismic noise sources activity, namely the LKCI seismic site. The seismic noise level at a frequency of 5-10 Hz originating from human activities and vehicles is the highest indicated by the LKUCM seismic site.
IDENTIFICATION OF LOCAL ACTIVE FAULTS IN MAINLAND GORONTALO REGION BASED ON FOCAL MECHANISM ANALYSIS Pertiwi, Imanuela Indah; Rifai, Listya Dewi
Jurnal Geosaintek Vol. 10 No. 3 (2024)
Publisher : Institut Teknologi Sepuluh Nopember

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12962/j25023659.v10i3.2217

Abstract

One of the nations that experiences devastating earthquakes frequently is Indonesia. Local active faults on land are one of the causes of these earthquakes. New information on the purported presence of local active faults can be obtained from the quantity of small-magnitude earthquake occurrences. By analyzing the focal sphere mechanism, small-scale earthquake data are used to identify local active faults in the Gorontalo area. The minor magnitude earthquakes (M<5) that struck the Gorontalo region in February 2023 and were recorded eleven events at the BMKG- Gorontalo Geophysical Station that were used in this investigation. he resulting focus sphere diagram can be used to ascertain the faults or strike direction propensity. The focal mechanism of the earthquake in the Pohuwato region demonstrates the Oblique Thrust Fault's inclination toward a northeastern-southern strike orientation. The tendency of the strike orientation of the east-west-oriented Oblique Thrust Fault, which is the focal mechanism of the earthquake that happened in Buol, also demonstrates the same thing. According to the Gorontalo Fault diagram provided by the National Earthquake Study Center, the focal mechanism of the earthquake in Cluster A (earthquake numbers 1,6,9), the Gorontalo region, also demonstrates the strike direction of the Northwest-Southeast-oriented Oblique Thrust Fault. The earthquake occurrences in cluster B (Pohuwato area), earthquake numbers 2,3,8, and cluster C (Buol area), earthquake numbers 4, 5,7, raise the possibility of a new local active fault on the Gorontalo region's mainland. The Gorontalo region's suspicion of the existence of local active faults is strengthened by the monitoring of earthquake intensity based on occurrences that occurred between March 2023 and March 2024. Over the course of a year, there are nine to twenty-seven earthquakes with a magnitude of less than five (M<5). These seismic occurrences provide credence to the theory that Pohuwato and Buol, Gorontalo, have local active faults.