Identification of Earthquake Hazard Vulnerability in Bengkaung Village, West Lombok Using Geomagnetic Methods

An earthquake disaster is an event that causes various damage and loss of life. This study aims to determine the vulnerability of earthquake hazards in Bengkaung Village, West Lombok Regency. The method used in this research is the geomagnetic method. The results of this: study indicates the value of the magnetic field anomaly in the range of -1100 nT-1500 nT. 2D modeling with 4 paths shows that the study area is dominated by 5 rock layers with a susceptibility range between (0.013 - 6.21)×10^(-3) in SI, which consists of sandstone, clay, fractured andesite lava, fresh andesite lava. and granite. The highest vulnerability to earthquake hazards is in the southern part of Bengkaung Village, due to the presence of a cohesive soil type (like clay) on the surface of the study area, coupled with the presence of intrusions and faults. Meanwhile, the western part of Bengkaung Village and the northern part of the Bengkaung area have a relatively smaller earthquake hazard vulnerability than the southern part. This is because the western and northern parts have the main layer of non-cohesive soil (sandstone) which has high shear strength and becomes a damper in wave propagation when an earthquake occur

Subsurface Structure Models Of Sumbawa Island And Flores Back Arc Thrust Based On Gravity Data

Based on the BMKG report on Wednesday, July 29, 2018, at 05.47 WIB, an earthquake with a magnitude of 6.4 SR occurred at the epicenter at a depth of 24 km and was 47 km northeast of the island of Lombok. They are allegedly originating from the Back Arc Thrust Flores, the interaction between the Indo-Australian Plate and the Eurasian plate. This study aims to analyze the subsurface structure of the island of Sumbawa and Flores sea based on the distribution of density values. The analysis was carried out by modeling the subsurface structure based on regional gravity field anomaly data. The data used is secondary data downloaded from the topex.ucsd.edu page 18,400 measuring points. Data processing consists of data correction, separation of anomalies, determination of the Second Vertical Derivative (SVD) value, and 3D and 2D inversion modeling. The data corrections performed are Bouguer correction and terrain correction to produce the total gravity anomaly value. Upward continuation is used to separate regional anomalies and residual anomalies. Analysis of the Second Vertical Derivative (SVD) value was carried out to identify rock contact positions and fault structures. The 3D inversion modeling is done by making a mesh model, and to get a 2D cross-section, six slices are used in the 3D model. The results of the 3D model and 2D cross-section, namely the island of Sumbawa to the Back Arc Thrust zone of Flores, consists of 3 main layers comprised of the upper crust with a density of 2.29 gr/cc - 2.63 gr/cc, the middle crust with a density of 2.64 gr/cc - 2.90 gr/cc, and the lower crust with a density of 2.91 gr/cc - 3.14 gr/cc, and based on the model and SVD value, it shows that the Flores back fault, the reverse fault type, starts at a depth of ± 26 k

Penentuan Lapisan Batuan Bawah Permukaan di Desa Malaka Kabupaten Lombok Utara Menggunakan Metode Geolistrik

Desa Malaka merupakan salah satu desa yang mengalami kerusakan berat akibat gempa Lombok yang terjadi pada tahun 2018. Diduga terdapat tanah lunak di Desa Malaka sehingga penelitian mengenai keberadaan lapisan batuan bawah permukaan perlu dilakukan untuk mengetahui lapisan batuan yang berpotensi menimbulkan kerusakan ketika terjadi gempa. Metode geofisika yang digunakan adalah metode geolistrik dengan konfigurasi Wenner-Schlumberger. Berdasarkan hasil penelitian, diperoleh bahwa bentuk lapisan batuan bawah permukaan didominasi oleh lapisan tanah lunak yang terdiri dari tiga lapisan batuan yakni lapisan pertama merupakan batu pasir, lapisan kedua merupakan alluvium, lapisan ketiga merupakan jenis batuan mengandung air asin dan lapisan lempung. Zona lemah yang didominasi lapisan lempung terindikasi sebagai rekahan dan sesar yang terdapat di Dusun KLUI, di Dusun Nipah, di Dusun Malimbu, dan di Dusun Pandanan berupa rekahan dan sesar dengan adanya struktur batuan yang tidak menerus.

Pemetaan Sebaran Endapan Debris Avalanche Menggunakan Metode Geolistrik di Kawasan Pantai Kwangwai Kabupaten Lombok Timur

Debris avalanche merupakan salah satu dampak negatif dari letusan gunung berapi. Debris avalanche terdiri dari material runtuhan penyusun tubuh gunung berapi, apabila longsoran tersebut dalam jumlah besar dapat mengakibatkan kerusakan pada bangunan yang ada di dataran rendah. Berdasarkan observasi yang telah dilakukan, diketahui bahwa pada kawasan Pantai Kwangwai terdapat gundukan yang merupakan hasil endapan debris avalanche yang tersusun dari blok – blok andesit. Penelitian ini bertujuan untuk menegtahui sebaran endapan debris avalanche dan karakteristiknya berdasarkan metode geolistrik resistivitas 2D konfigurasi Wenner. Berdasarkan pemodelan inversi 2D diperoleh hasil, bahwa pada kawasan Pantai Kwangwai terdapat material endapan debris avalanche berupa blok andesit yang memiliki nilai resistivitas 95 – 3000 ohm.m dengan ketebalan mencapai 18 m. Material tersebut tersebar hampir 90 % dari luas area daerah penelitian yaitu 1,82 km2, endapan debris avalanche yang terdapat di daerah penelitian merupakan endapan debris avalanche block yang  materialnya bersifat  tidak jenuh ai

Determination and Mapping of the Causes of High Risk of Earthquake Hazards Using Geoelectrical Data in Bengkaung, Batu Layar, West Lombok Indonesia

The Bengkaung area, Batulayar District, West Lombok is suspected to be very vulnerable to the risk of earthquake hazards. However, in this area no scientific research, either geological or geophysical, has ever been carried out regarding this hazard. How are the physical characteristics of the lithology and structure in the area to the risk of earthquake disaster? The purpose of this study was to determine the physical characteristics of the lithology and subsurface structures that were validated by the level of damage. The method used is the geoelectric method and local building damage data. The results of the 2D geoelectric anomaly modeling show the characteristics of the subsurface lithological layers in the form of sand, sandstone, clay, andesite lava faults, fresh andesite lava, and granite. The fault was detected in the center of the study area in a north-south direction. Earthquake hazard analysis shows that the cause of the high risk of earthquake hazard in Bengkaung Village is the presence of faults and cohesive lithology. The highest potential risk is in the southern part of Bengkaung Village. The southern area of ​​Bengkaung Village is dominated by clay that has cohesive properties, especially on the surface. The western and northern parts of Bengkaung Village have medium and low vulnerability to earthquake hazards. The last two areas are dominated by non-cohesive soils in the form of sandy soils and lapilli pumic

A Platform for the Analysis of Qualitative and Quantitative Data about the Built Environment and its Users

There are many scenarios in which it is necessary to collect data from multiple sources in order to evaluate a system, including the collection of both quantitative data - from sensors and smart devices - and qualitative data - such as observations and interview results. However, there are currently very few systems that enable both of these data types to be combined in such a way that they can be analysed side-by-side. This paper describes an end-to-end system for the collection, analysis, storage and visualisation of qualitative and quantitative data, developed using the e-Science Central cloud analytics platform. We describe the experience of developing the system, based on a case study that involved collecting data about the built environment and its users. In this case study, data is collected from older adults living in residential care. Sensors were placed throughout the care home and smart devices were issued to the residents. This sensor data is uploaded to the analytics platform and the processed results are stored in a data warehouse, where it is integrated with qualitative data collected by healthcare and architecture researchers. Visualisations are also presented which were intended to allow the data to be explored and for potential correlations between the quantitative and qualitative data to be investigated

Analysis of Groundwater Decline and Land Subsidence by using of Microgravity and Vertical Gravity Gradient Over Time Method

Studies have been conducted to identify the occurrence of subsidence, a decline of groundwater, and to model the causes of subsidence in areas of Jakarta based on response of microgravity anomaly and vertical gravity gradient over time. Based on the processing and interpretation of gravity data advance of the time concluded that by using a combination of time lapse microgravity and its vertical gradient have been able to localize the source of the gravity anomaly and the results are strongly support the results of filtering to separate the source of the anomaly. The subsidence that occurs predominantly due to resettlement (in West and North Jakarta), caused by the extraction of groundwater and resettlement (in Central and East Jakarta), and dominated due to the extraction of groundwater (in South Jakarta).Keywords : Groundwater, time lapse micogravity, time lapse vertical gradient, resettlement, subsidenc