Abstract The purpose of this research is to analyze of tectonic earthquake parameter value in Bengkulu Province based on single-station data of BMKG Kepahyang, Bengkulu and multi-station data of BMKG Center, Jakarta along with determine its distribution model from January 2005 until March 2009. The results show that distance difference of mean earthquake epicenter is 28.60 km. The distribution of earthquake in Bengkulu Province from January 2005 until March 2009 had majority distributed in Hindia Oceanic and its mean earthquake included shallow earthquake (<70 km). Keywords: Earthquake parameter, single-station, multi-station, magnitude, and epicenter.
The accurate prediction and prevention of earthquakes remains challenging. Consequently, the primary approach to mitigate the impact of earthquakes is through disaster risk reduction efforts. One significant strategy involves conducting seismic vulnerability analyses based on disaster scenarios. This study aims to identify and map areas with varying levels of seismic vulnerability, analyzing the factors contributing to vulnerability in the South Bengkulu Regency. Secondary data, including peak ground acceleration (PGA) values, were collected, along with microtremor data obtained through the Horizontal to Vertical Spectral Ratio (HVSR) method. The recorded microtremor data serve as input parameters for PGA, Modified Mercalli Intensity (MMI), Seismic Vulnerability Index (Kg), shear wave velocity (Vs), and the time-averaged shear wave velocity for the first 30 m depths (Vs30) values. The findings reveal that, overall, seismic vulnerability in the South Bengkulu Regency can be categorized as low. However, specific areas, particularly in the southwestern and northeastern zones, exhibit relatively higher levels of vulnerability. The heightened vulnerability in these areas is attributed to elevated PGA values, despite the region's generally high soil density, which acts as a mitigating factor against earthquake threats.
Penelitian ini bertujuan memodelkan sistem panas bumi bawah permukaan baik secara vertikal (sounding) maupun lateral (mapping) dengan metode geolistrik tahanan jenis di daerah prospek Gunungapi Hulu Lais bagian utara (Desa Karang Dapo dan Desa Semelako).
Penelitian ini bertujuan untuk mengidentifikasi lithologi batuan yang berhubungan dengan struktur perlapisan batuan bawah permukaan berdasarkan kontras resistivitas medium dan menginterpretasi sebaran resistivitasnya. Akuisisi data di lapangan menggunakan peralatan CSAMT model Stratagem 26716 Rev. D. Data diolah dengan menggunakan transformasi Bostic. Hasil yang diperoleh menunjukkan bahwa daerah survai yang terletak di Kasihan disusun oleh lithologi yang merupakan satu satuan batu pasir yang terdiri dari konglomerat pasir dan batu pasir vulkanik, intrusi batuan beku andesit di beberapa daerah masih berhubungan satu sama lainnya yang menembus batu pasir vulkanik dan konglomerat. Adapun sebaran mineral phirit ke arah Baratdaya-Timurlaut dan mineral phirit di daerah ini mengandung besi yang cukup banyak.
Abstrak. Provinsi Sumatera Utara merupakan salah satu provinsi yang juga sering terjadi gempa bumi, karena wilayahnya terletak pada pertemuan dua lempeng tektonik yaitu lempeng Indo-Australia dan lempeng Eurasia. Penelitian ini bertujuan untuk mengetahui perulangan gempa yang terjadi di Provinsi Sumatera Utara berdasarkan dari b-value serta kaitan b-value dengan magnitudo dan frekuensi gempa bumi. Hubungan b-value dengan magnitudo dan frekuensi gempa bumi dianalisis dengan metode likelihood. Data gempa bumi diambil dari website USGS, yaitu data dari tahun 1926-2023 yang berjumlah 4242 kejadian gempa bumi dengan menggunakan software Z-map. Data tersebut dilakukan cluster sehingga jumlah data menjadi 3033 data dengan magnitudo 3,0 sampai magnitudo 8,0 dan kedalaman 0-300 km pada koordinat episenter 1º- 4º LU dan 95º-105º BT. Berdasarkan data-data tersebut didapatkan b-value = 0,0939+/-0,02 dan a-value = 7,55, a-value (annual) = 5,56 serta nilai Magnitude of Completeness = 4,45 dapat menggambarkan tingkat stress yang sedang terjadi, b-value merupakan nilai yang menunjukkan tingkat kerapuhan suatu batuan. Dari data yang dihasilkan pada daerah Sumatera Utara, gempa yang sering terjadi adalah pada magnitudo 5,0 dan magnitudo 6,0 yang hampir meliputi semua daerah Sumatera Utara. Semakin tinggi nilai b pada suatu wilayah, maka akan semakin tua dan rapuh batuannya sehingga aktivitas seismik di wilayah tersebut juga akan semakin besar. Nilai b yang rendah itu merupakan daerah yang memiliki tingkat stress yang tinggi yang artinya wilayah tersebut memiliki peluang yang tinggi untuk terjadinya gempa-gempa besar. Abstract. North Sumatra Province is one of the provinces where earthquakes often occur because the region is located at the meeting point of two tectonic plates, namely the Indo-Australian plate and the Eurasian plate. This research aims to determine the recurrence of earthquakes that occur in North Sumatra Province based on the b-value and the relationship between the b-value and the magnitude and frequency of earthquakes. The relationship between b-value and earthquake magnitude and frequency was analyzed using the likelihood method. Earthquake data was taken from the USGS website, namely data from 1926-2023, totaling 4242 earthquake events using Z-map software. The data was clustered so that the total data became 3033 data with a magnitude of 3.0 to 8.0 magnitude and a depth of 0-300 km at epicenter coordinates 1º-4º N and 95º-105º E. Based on these data, b-value = 0.0939 +/- 0.02 and a-value = 7.55, a-value (annual) = 5.56 and Magnitude of Completeness = 4.45 can describe the level of stress that is occurring, b-value is a value that shows the level of brittleness of a rock. From the data produced in the North Sumatra area, the earthquakes that frequently occur are at magnitude 5.0 and magnitude 6.0 which almost covers all areas of North Sumatra. The higher the b value in an area, the older and brittle the rocks will be, so the seismic activity in that area will also be greater. A low b value indicates an area that has a high stress level, which means the area has a high chance of large earthquakes occurring.
This study uses the gravity method to assess the characteristics of the Manna segment fault, a part of the Sumatran fault. This research aims to contribute to the existing knowledge by providing additional insights into the fault's characteristics, which is essential for future disaster mitigation efforts. The Manna segment fault is geographically situated between coordinates 4.4⁰S - 3.9⁰ S and 102.7⁰ E – 103.2⁰ E, making this area prone to earthquake hazards. The gravity anomaly data, including free air and topography, were collected from 62,501 data points. The Simple Bouguer Anomaly (SBA) values obtained ranged from 25 mGal to 95 mGal. By utilizing the Second Vertical Derivative (SVD) method and dividing the study area into three regions with multiple sections, the analysis revealed that the minimum and maximum SVD values were relatively similar. This suggests that the Manna fault can be classified as a strike-slip fault, with SVD values ranging from Elkins-20 mGal to 6 mGal. The study identified branches of the main fault in regions 2 and 3 based on the SVD map. Overall, this study enhances our understanding of the Manna segment fault, providing valuable insights into its characteristics and contributing to future disaster mitigation efforts.
The coastal areas of North Bengkulu Regency, particularly Urai Village, have been severely impacted by widespread abrasion, posing a high risk of coastal erosion within Bengkulu Province. This study aims to assess the extent of coastal degradation and support disaster mitigation efforts by investigating the properties and structure of rocks using geophysical methods, specifically the Multichannel Analysis of Surface Waves (MASW). The research focuses on determining shear wave velocity (Vs) to model the rock layers and produce a stratigraphic profile with a minimal misfit value. The obtained Vs30 values, ranging from 146 m/s to 603 m/s, indicate that the coastal region primarily comprises soft soils, which are highly susceptible to deformation, including abrasion. These findings provide essential data for understanding the underlying causes of coastal erosion and contribute to future disaster mitigation strategies.
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