Bulletin of Earth Sciences of Thailand

Kinematic history of the thrust fault-related calcite veins at the Indochina margin, Thailand

Thu, 29 Aug 2024 00:00:00 +0700

The study area is in Lam Sonthi district, Lop Buri province, which is part of the Indochina margin. Calcite veins in the area are usually associated with thrust faults in the Mesozoic Phu Kradung formation at the western margin of Indochina in Thailand. Veins are crucial structures for unraveling the geological history of the host rock. The shape, orientation, and internal structures of veins reveal information about palaeo-stress fields, deformation kinematics, and fluid pressure. Therefore, in this study, structural and microstructural analyses of the calcite veins were conducted to examine the kinematics of the veins and their related geological structures within the Phu Kradung Formation in the Lam Sonthi area. The result suggests that the Phu Kradung Formation underwent gentle folding concurrently with the development of east- and west-dipping calcite veins. The fibrous nature of the calcite within these veins suggests shear components influenced by an east-west compression regime. The west-dipping veins often branched out into the east-dipping veins. Subsequently, thrust faults developed parallel to the earlier east- and west-dipping calcite veins. Later, vertical calcite veins intersected the pre-existing structures. These deformations were tectonically influenced by Eocene-Oligocene escape tectonics in Southeast Asia.

The Quantifying Crustal Deformation Caused by the Cianjur Tectonic Earthquakes Magnitude 5.6 through InSAR and GNSS Technology

Muhammad Hanif, Sakpod Tongleamnak — Sun, 25 Aug 2024 00:00:00 +0700

Indonesia, an archipelagic country situated within the volatile Ring of Fire and the convergence of multiple tectonic plates, frequently experiences seismic activity. These earthquakes have led to alterations in the Earth's surface layers and even damage to the land. The Cianjur earthquake, which occurred on November 21, 2022, was a shallow crustal tectonic earthquake of the mainshock variety, followed by a series of aftershocks. The objective of this research is to conduct deformation mapping before and after the Cianjur Magnitude 5.6 earthquake. The research employs remote sensing technology, specifically interferometric synthetic aperture radar (InSAR), in conjunction with global navigation satellite system (GNSS) analysis techniques. The results have yielded valuable insights into the spatial distribution of vertical tectonic deformation through InSAR and GNSS analysis, revealing that the co-seismic deformation reached a maximum value of 5.87 cm, concentrated in the Cugenang sub-district. In contrast, GNSS station data recorded co-seismic deformation of 4.6 cm and horizontal deformation of approximately ±12 cm, directed southeastward. These findings indicate that aftershocks had a more significant impact on deformation in the Cianjur region, particularly around the Cugenang fault area. Variations in the source of the main earthquake and subsequent aftershocks substantially influenced deformation patterns and the direction of horizontal deformation.

Susceptibility Investigation of Debris Flow Using Topographic Index in the Uttaradit Province

Pakaporn Manajaroensook , Santi Pailoplee — Sun, 25 Aug 2024 00:00:00 +0700

Uttaradit Province, situated in Thailand's lower northern region, faces significant risks from geohazards such as debris flows, landslides, and flooding. These hazards pose a serious threat to both people and property. The area's susceptibility to debris flows is influenced by several topographic factors, including steep mountain slopes and numerous mountain-front outlets. In this study, we used the Frequency Ratio (FR) method to identify and map areas susceptible to debris flows in Uttaradit Province. We analyzed topographic indices related to debris flow activity using terrain data derived from a 12.5-meter resolution Digital Elevation Model (DEM). The FR was calculated using ten parameters indicative of areas vulnerable to debris flows. These parameters included: i) Distance to road, ii) Plan curvature, iii) Terrain ruggedness index, iv) Profile curvature, v) Slope, vi) Melton ruggedness number, vii) Topographic wetness index, viii) Stream power index, ix) Elevation, x) Lithology. The results allowed us to categorize the debris flow susceptibility in Uttaradit Province into five levels. Areas with high and very high susceptibility were mainly located in the plains of the southwest and the Khao Phi Pan Nam region. In contrast, the northeastern, northwestern, and northern parts of the province were identified as having medium and low susceptibility.

GIS Analysis of Route along the Thailand-Myanmar Border using Topographic Data: Implication for Illegal Immigration

Bongkod NaBhadalung, Santi Pailoplee — Sun, 25 Aug 2024 00:00:00 +0700

This study delves into the intricate issue of illegal border crossings from Myanmar into Thailand, with a particular focus on the Thailand-Myanmar border region, renowned for its geographical diversity and porous boundaries. Employing Geographic Information Technology Systems (GIS) and Least Cost Path (LCP) analysis, the research aims to identify potential routes employed by individuals engaging in illegal border crossings. The study reveals that Tak Province in Thailand, specifically the Mae Sot District, stands out as a primary entry point for illegal immigrants. This phenomenon can be attributed to the region's distinctive geographic features and limited patrol capabilities. It also identifies other high-density routes in Chiang Rai, Kanchanaburi, and Ranong Provinces. Additionally, through a comprehensive examination of the Kanchanaburi-Myanmar border area, the research highlights the Ban Phra Chedi Sam Ong area as a designated high-risk zone for illegal immigration. Lastly, the research results illuminate areas that present less favorable conditions for foot travel when it comes to illegal border entry, particularly Ratchaburi and Phetchaburi provinces. These regions are characterized by mountainous terrain and a lack of border communities, rendering them less accessible and unsuitable for travel and illegal activities. In conclusion, this research significantly contributes to a deeper understanding of the dynamics surrounding illegal border crossings between Myanmar and Thailand.

Application of MEPBAY for beach stability evaluation: a preliminary test on Rayong Beach, Eastern Thailand

Siraset Apichanungkul, Santi Pailoplee, Montri Choowong — Sun, 25 Aug 2024 00:00:00 +0700

The coastline of Rayong Province, eastern Thailand has been subjected to erosion for decades. Basically, there are two main reasons for erosion, including natural processes such as coastal currents, tides, waves, storms, and monsoons and climate change and human activities such as the failure of sea wall construction. The objective of this study was to apply the MEPBAY program to test the stability of beaches in Rayong Province where several sea walls were constructed. As a result, beaches exhibiting static planform equilibrium remain relatively unaltered except during monsoons. Beaches subject to dynamic equilibrium are primarily situated near river mouths, where their condition hinges on sediment discharge from the rivers. Conversely, the unstable of beaches arises from their reliance on hard structures, necessitating adjustments for the beach to achieve a state of static equilibrium.

Preliminary geotourism study of laterite attraction in Kamphaeng Phet Province, northern Thailand

Thitiphong Waikhamnuan, Sakonvan Chawchai, Raphael Bissen, Montri Choowong — Sun, 25 Aug 2024 00:00:00 +0700

A UNESCO World Heritage Site in Kamphaeng Phet, which once was a part of the Sukhothai Kingdom, showcases stunning architecture constructed from laterite with rich cultural traditions, making it a popular tourist destination (e.g., temples, pagodas, ponds, and walls). These attractions are surrounded by several laterite quarries, which are believed to have been used in the construction of those places. They carry significant scientific and historical importance, positioning them as potential geoarchaeological tourism destinations. This research primarily focuses on the geological features in the vicinity of these laterite attractions. Seven specific laterite attractions were selected in Kamphaeng Phet, including (1) Kamphaeng Phet Historical Park within the city walls, (2) Kamphaeng Phet Historical Park in the Aranyika region, (3) Nakhon Chum Historical Site, (4) Wat Nong Pling, (5) Blue Pond Kamphaeng Phet, (6) Tham Nang Thong archaeological site, and (7) Wat Khanathi Si Wachiraram. Guidelines for geotourism development were thoroughly analyzed for these sites. Additionally, the study conducted evaluations of the attractions, singling out Kamphaeng Phet Historical Park and Nakhon Chum Historical Site as possessing higher geoheritage values. Furthermore, a SWOT analysis was performed to establish management priorities. Finally, a tourist route map connecting between laterite attractions and laterite sites in Kamphaeng Phet was generated, providing valuable information and knowledge about the history and geology of laterite in the province. This research contributes to the increased geosite potential in the area of the national historical park, potentially paving the way for it to become a geopark.