Arm Of Sulawesi Research Articles

Gravity field and crustal structure of the Eastern Arm of Sulawesi and the Banggai Archipelago, Eastern Indonesia

The occurrence of extensive ophiolite masses and the development of the Batui-Balantak foreland thrust-fold belt on the Eastern Arm of Sulawesi can be attributed to the geologic process in the Neogene period when the Sulawesi Island Arc and the Banggai-Sula collided. Following the convergence, crustal fragments were further adjusted on a regional scale. This adjustment involved the rotation of crustal fragments into strike-slip faults on Sulawesi Island and the formation of extensional faults in the Banggai Archipelago. The analyses of the gravity field in the region of the eastern Sulawesi and Banggai Archipelago have yielded models that can potentially be interpreted as a representation of the underlying crustal structure in the region. The models can also be understood in a way that has consequences for tectonics. The tectonic episodes have played a significant role in the formation and development of sedimentary basins within the region. The primary objective of this study was to investigate the crustal structures of the Eastern Arm of Sulawesi and the Banggai Archipelago by means of analyzing gravity profiles. The findings of the analysis suggest that there is a slight thickening observed in the crustal block beneath the central portion of the eastern arm region. In addition, this area exhibits significant fracturing and severe attenuation. Furthermore, the crustal block has a dipped north-eastward trend in response to the ascent of the Molucca Sea oceanic crust.

Facies Analysis and Sequence Stratigraphy of Plio-Pleistocene Fan Delta Deposits in the East Arm Sulawesi, a case study of Biak Formation, Luwuk, Banggai

Abstract Fan delta deposits were found widespread in the east arm of Sulawesi as the area experienced tectonic uplift during Plio-Pleistocene continental collision, known as Bongka Formation in the western part and Biak Formation in the eastern part. One of key outcrops for Biak Formation was observed in Biak Village, North Luwuk District, Banggai Regency, thus served as the lithotype location for the Biak Formation. The outcrop was a roadcut and had a 50 m long and 25 m high. In general it shows a coarse-grained heterolithic inclined strata dipping southward and overlain by horizontal strata of similar facies. Its sequence stratigraphy was analyzed by examine its facies, facies association, petrography, and paleontology, along a 1:100 scaled measured section. Six lithofacies were identified, namely conglomeratic coralline limestone, conglomeratic coralline limestone, parallel bedding – gradation conglomerate-sandstone, gravely sandstone, conglomerate-sandstone – conglomeratic corraline limestone and gradation conglomerate-sandstone with horizontal bedding. Their lithofacies deposited during Late Pliocene in a transition – inner neritic environment. Their facies association made several depositional system tracts, showing a complete cycle of Highstand System Tract (HST), Sequence Boundary/Correlative Conformity (SB/CC), Lowstand System Tract (LST), Transgressive System Tract (TST), Transgressive Surface (TS) later capped by younger HST and LST. Result of this study suggesting repetitive cyclic depositiona tracts dictated by sea-level eustacy and tectonic uplift. This location served as an ideal outcrop as a textbook example to study sequence stratigraphy in an outcrop scale.

Facies of Quaternary Sediments In Bunga Village, North Luwuk District, Banggai Regency, Central Sulawesi

Abstract The distribution of Quaternary sedimentary rock deposits in Indonesia is quite extensive, and one of them is in the Quaternary coral reef units, which are evenly distributed along the eastern arm of Sulawesi. The research was conducted in Bunga Village, North Luwuk District, Banggai Regency, Central Sulawesi Province. This research was motivated by the lack of geological data, so the topic of developed facies became an interesting topic to be researched. Data was collected from a cliff at the coordinates 0053′57,57.1″N-122054′43′6″E. Stratigraphic measurements aim to determine the facies, depositional environment, and sedimentation mechanisms developed in the study area. The research was conducted using the method of field data collection and laboratory analysis. Collecting field data was carried out with measured stratigraphic with a 1:100 scale and taking several rock samples. Laboratory analysis was carried out in paleontological and petrographic analysis, which was carried out to determine the composition of the constituent rock and fossil identification, especially foraminifera in thin sections of rock that were selected. Based on the study’s results, the total rock layers measured in the study area were 15 m. Facies found in the stratigraphic path of the study area are floatstone facies, rudstone facies, allochemic sandstone facies, polymict conglomerate facies. The type of deposition environment of limestone and allochemic sandstone in the study area is on the foreslope, while the conglomerate facies is included in the fan delta deposition environment. Overall, the sedimentation dynamics in this area are in a high energy environment, indicating that the facies that developed were deposited with a sediment gravity flow mechanism.The results of the analysis of fossils found Cyclammina cancellata sp., Orbulina universa sp., Globigerina bulloides sp., and Trilobatus immaturus sp., which indicates the limestone in the study area was deposited in the Late Pleistocene to early Holocene.

Stratigraphy of Salodik Formation in Batutambung section, Toili, Luwuk, Central Sulawesi

Abstract Salodik Formation is one of the formations representing a continental drift sequence prior to the collision of Banggai Basin, and it was widely cropped out in the East Arm of Sulawesi. The published geological maps of Luwuk dan Batui describe the Salodik Formation as massive and bedded limestone with marl intercalated and sandstone in the lower part, ranging from Eocene to Late Miocene. In Batutambung, Toili, the geological maps showing the Salodik Formation distributed in a NW-SE trend between two ophiolitic land masses, and suggesting intensive tectonic deformation along the trend. Preliminary geological investigations in this area show that Salodik rock sequences varied from other Salodik outcrops in different areas. Detailed stratigraphic measurements and rock sampling have been carried out along the road connecting Toili and Ampanan Tete., yielding a measured stratigraphy of 70 m vertically thick. Nine lithofacies were identified, i.e., coarse-grained sandstone (cS), micritic sandstone (mcS), fine-medium-grained sandstone (fmS), sandstone with coal spar (SMms), Mudrock (mM), micritic mudrock (mcM), Mudstone (MS), Wackestone (WS) and Packstone (PS). Facies association shows the rock sequence has shallowing upward or prograding pattern with depositional environment varies from an open marine, tidal channel, shoal, and restricted marine/ lagoon Based on foraminifera and nannofossil analysis, Salodik Formation in Batutambung section was deposited in Early Miocene (N6 or NN4-NN6), with paleobathymetry from middle to outer neritic. Based on its age and lithology character, the Salodik Formation in Batutambung is equivalent with Matindok Formation in Tomori PSC.

Rolling with the punches—How competition shapes the morphology of small passerines on small islands

AbstractAimWallacea is a global biodiversity hotspot and Sulawesi is the largest island in this region, notable for a high proportion of endemic species. The Wakatobi archipelago, off the southeastern peninsular arm of Sulawesi, is home to several endemic bird species. Although islands are known to influence the morphology of their resident species, competitive interactions also exert strong influences on morphology. Here, we consider the contributions of both islands and competitors on two morphological traits of two bird species in a small passerine guild found on the Wakatobi islands.LocationWakatobi archipelago, Sulawesi Tenggara, Indonesia.TaxonWakatobi White‐eye (Zosterops flavissimus) and Wakatobi Sunbird (Cinnyris infrenatus).MethodsWorking with morphological measures (from netting studies), population density metrics (from transect surveys) and fundamental data from islands (area, distance from mainland and elevation), we investigated (by means of multiple linear regression) which terms best explained variation in the body size and bill size of two small passerine birds endemic to the Wakatobi islands.ResultsBoth island metrics and competitor presence/density were useful in describing the variation in body size of both bird species. However, only competitor presence/density was useful in describing variation in bill size of the birds. The best models describing variation in these traits included terms representing both interspecific and intraspecific competition.Main ConclusionsOur findings indicate that simple island metrics may be useful in predicting some of the variation in some functional traits of island species. However, in this example, simple island metrics were insufficient to explain the full variation in body size of endemic birds across the Wakatobi archipelago and were of no use in predicting the variation in their bill size. As bill morphology frequently dictates diet and feeding niche, it is a trait which may determine population divergence and speciation. If simple island metrics fail to describe such diversification, it is surely important to capture that information in other ways.

The effect of artificial light at night on a nocturnalprimate.

Anthropogenic disturbance is a major threat to biodiversity. An anthropogenic disturbance that is rarely addressed for nonhuman primates is the effect of artificial light at night (ALAN) which is defined by the spread of artificial lighting at night which eliminates natural darkness. Artificial light at night can result from streetlights, or indirectly from sky glow (artificial light that is scattered and reflected back to earth by the atmosphere). Research has demonstrated that artificial lighting causes changes in animal behavior, reproductive success, survivorship, as well as can alter the composition of the communities. The goal of this paper is to explore how the behavior of spectral tarsiers, Tarsius spectrumgurskyae, is modified in response to artificial light. We conducted this study at Tangkoko Nature Reserve on the easternmost tip of the northern arm of Sulawesi, Indonesia. The results of this study suggest that in response to artificial light tarsiers increase their time spent travelling and foraging, left their sleeping sites earlier and returned to them later thereby extending their daily activity time. The tarsiers also left their sleeping trees at lower heights, gave fewer vocalizations and fewer alarm calls each night in response to the additional artificial light. The tarsier's lengthened night might be leading to a change in interspecific competition for food as well as increase the ability of potential predators to locate the tarsiers. Additional research on the effect of ALAN on primates is clearly needed.

Tsunami Modeling Study in Geological Disaster Mitigation in the Kwandang Region

The northern coast of the northern arm of Sulawesi is the meeting place of 3 plates that collided with each other during the Neogene period. This condition makes the northern part of Gorontalo, especially Kwandang sub-district, very prone to earthquakes with magnitudes above 6 on the Richter scale (SR), which is one of the triggers for tsunamis. In the period from 1990 - 2008, there were 4 major earthquakes recorded in Gorontalo, namely 1990 (7.3 SR), 1991 (7.1 SR), 1997 (7.0 SR) and 2008 (7.7 SR). Therefore, further research is needed on the return period of the earthquake and the tsunami model that occurs and the sign of tsunami occurrence in the past. This research aims to determine the return period of the earthquake that caused the tsunami and the tsunami model as well as the sedimentology analysis of paleotsunami deposits. The calculation of the earthquake return period uses the Guttenberg-Richter method. Modeling calculations were carried out using the COMCOT numerical model. This model performs calculations by solving shallow water equations in the form of both linear and non-linear equations. Paleotsunami deposits were analyzed using the sedimentology method. The results of the calculation at a magnitude of 6.0 SR show that within 100 years, the study area has a chance of a potentially destructive earthquake of 1.14024978. The results of modeling the tsunami-prone zone, obtained an area of 165.598389 ha. And obtained paleotsunami deposits containing foraminifera with a sediment thickness of 14 cm.

Sandstone Provenance of Walanae Formation as a Parent Rock in Bulukumpa area, Bulukumba Regency, South Sulawesi

The Walanae Formation has a wide distribution in the southern arm of Sulawesi, this rock formation was deposited during the formation of the basin due to the Walanae strike-slip fault. The Walanae Formation in the study area comprises sedimentary rocks and pyroclastic rocks, which give different soil characteristics. This study aims to determine the types of sandstones, rocks of origin, and provenance of sandstones in the study area by using spot sampling at representative stations and petrographic analysis. The sandstones of the study area are divided into two groups based on Folk (1974), namely arkose lithic and feldspathic litharenite. Based on the type of quartz, rock fragments, and associated minerals, the origin of the sandstones in the study area are plutonic igneous rocks, volcanic rocks, sedimentary rocks, and metamorphic rocks. The results show that the types of provenance sandstones in the study area are magmatic arc and recycled orogenic.

Geologi Daerah Buyat Dan Sekitarnya, Kecamatan Kotabunan, Kabupaten Bolaang Mongondow Timur, Provinsi Sulawesi Utara

This research focuses on the eastern part of the northern arm of Sulawesi to understand the geological conditions, including geomorphology, lithology, stratigraphy, and geological structure. The goal is to determine the geological history and map the geological conditions to identify potential mineral resources. The research methods include a qualitative approach through field observations such as morphology, outcrop descriptions, lithology, geological structure measurements, stratigraphic relationships, as well as an inventory of natural resources and geological disaster risks. The quantitative approach involves calculations and analyses, including geomorphological analysis, petrography, paleontology, geological structure, stratigraphy, and the reconstruction of geological history. The research results identify four geomorphological units (karst, denudational, volcanic, alluvial) and six geological units at the research site. Andesite and volcanic breccia are the oldest units dating back to the Miocene. At the end of the Miocene, uplift and subsidence formed intrusive hills of diorite and limestone. Volcanic activity ceased in the Miocene. In the Pliocene, sandstone formed due to river transport. The rock formation process continues to the present, with alluvial deposit units resulting from the breakdown of rocks around the lake. Geological structure analysis reveals fault lines with the main stress direction from northwest to southeast. Relative fault data indicates fault inclination values suggesting the main stress direction is northwest-southeast. The geological history in the research area began in the Miocene with magmatism and tectonic activities, forming andesite and volcanic breccia units. This history extends to the formation of alluvial deposit units in the present. The research provides in-depth insights into the geological history and potential mineral resources in the region, serving as a foundation for further research.

Petrogenesis of Andesite Rocks in Datae Area, Sidenreng Rappang Regency, South Sulawesi Province

The research area is in the Datae Area, Watangpulu District, Sidenreng Rappang Regency, South Sulawesi Province. This study aims to determine the distribution of volcanic rocks, determine the crystallization phase based on petrographic analysis, and determine the type, magma affinity and tectonic environment based on geochemical data. The method used in this study was field data collection and rock sampling for analysis through petrographic analysis and geochemical analysis using the X-Ray Fluorescence (XRF) method by analysing the main elements, trace elements and rare earth elements (REE). The results of the petrographic analysis show that the rocks found in the field are volcanic breccia and ignimbrite. Volcanic breccia showed coarse-grained texture composed of angular to rounded andesite fragments and pyroclastic material fused together in a matrix. Meanwhile, ignimbrite showed fine grained texture with lapilli to boulder-sized fragments, poor sorting, open-packed and non-layered structure. Based on the Total Alkali Silika (TAS) diagram, AFM diagram, and binary diagram, the results of the geochemical analysis showed that the rocks found in the study area were andesite and trachy-andesite, while the magma affinity area is high-K calc-alkaline and shoshonitic. High-K calc-alkaline magmas are associated with subduction zones and are characterized by elevated levels of potassium and aluminum, while shoshonitic magmas are typically found in intraplate or back-arc settings, characterized by their distinctive potassium, sodium, and barium-rich compositions. The results from ternary diagram and geochemical Spider plots proved that the magma tectonic environment is island arc—continental arc basalt, indicating that the rock was formed in a subduction area. This research supports previous research regarding the tectonics of the western arm of Sulawesi, which stated that this area was formed by subduction.

ANALYSIS AND QUANTITATIVE ASSESSMENT OF GEODIVERSITY AT KARYA MURNI, GORONTALO, INDONESIA

Karya Murni is one of the areas in the northern arm of Sulawesi that has been tectonically influenced. Tectonic processes have implications for the formation of rocks and geological features that have the potential to be developed into geodiversity sites. The development of geological features as a geodiversity site in aspiring geopark Gorontalo can protect valuable geological features from frequent degradation. This research aims to analyze and conduct quantitative assessments of geological diversity in Karya Murni, Gorontalo. The research method used is field observation, laboratory analysis, and geodiversity assessment. Field observations included observing landform, collecting rock samples, and measuring geological structures. Field observations were also carried out to observe aspects of the geodiversity assessment which included science, education, tourism, and risk degradation. Laboratory analysis consists of geomorphological analysis, petrographic analysis, and geological structure data analysis. Geodiversity assessment uses the Geological Survey Center of Indonesia assessment. The results suggest that the geomorphology of the study area can be divided into four geomorphic units - the volcanic hills, denudational hills, Karst hills, and fluvial plain units. The stratigraphy of the research area is divided into four units from the age of the early Eocene to the Holocene - the andesite lava, volcanic breccia, reef limestone, and alluvial deposit units. The geological structure of the study area is a trending northeast–southwest to northwest–southeast. Active faults at the location of the study area consist of the Apitalawu normal fault. At recent states, generally geosites of the Karya Murni have moderate scientific values, the low educational and touristic values and high risk of degradation. The geodiversity potential of the research area can be utilized for further research and education.

Orogenic Gold Deposit in Metamorphic Rocks: Minerals and Structural Control at Rarowatu Area, Southeastern Arm of Sulawesi, Indonesia

This research aims to examine the relationship between hydrothermal alteration and mineralization (ore mineralogy) in the study area and geological structures in the deformation mechanism. The hydrothermal alteration was determined based on petrographic analysis, and ore mineralogy which was determined based on the ore microscopic analysis. The deformation mechanism is determined by paleo stress analysis using win-tensor, and the direction of principal stress on joints/veins and faults is calculated by the right-dihedron method. Hydrothermal alteration includes silicification, argillic, propylitic, and phyllic alterations; and ore mineralogy consists of stibnite, cinnabar, pyrite, chalcopyrite, sphalerite, covellite, hematite, and arsenopyrite at metamorphic rocks. The geological structure developed in the study area consists of shear fractures and Wumbubangka right Normal-slip Fault, which is accompanied by Wumbubangka right-slip lag fault and Wumbubangka reverse-slip fault formed in a simple shear mechanism. Crenulation, micro-folds, and porphyroblastic are also recognized in thin sections. The Wumbubangka right normal-slip fault, considered a syn-mineralization structure, formed the transpressional and transtensional geologic structures, forming the quartz vein parallel to and crosscutting the foliation. The correlation between surface geological structures and microstructures indicates that tectonic regimes have controlled the alteration and gold mineralization in the study area.

South Sulawesi Arm’s Evolution in the Past 50 million years and Its Impacts on the Geology and Geomorphology

ABSTRACT South Sulawesi Arm (SSA) is one of the four Celebes Island arms, geologically situated near the triple junction of Eurasia, India-Australia, and the Pacific Plate. This area has undergone unique geological history and evolution in the past 50 million years (m.y). SSA is distinct from the other Sulawesi arms as it is the only one attached to the Eurasian Plate, while others consist of ophiolite originating from the Philippines and Indo-Australian plates. This research aimed to explore the changes related to the geological evolution of SSA. It focused on explaining the following objectives: 1) Geological evolution of Sulawesi Island in sketch form since 50 m.y ago, divided into five intervals of 50–40, 40–35, 30–25, 20–15, and 10–5 million years, 2) uniqueness of SSA Evolution compared to other parts of Sulawesi Island and 3) geological and geomorphological conditions. Secondary data were collected from various literature reviews with ArcGIS Software 10.7 used to produce a model of SSA formation. The result showed that the evolution of SSA 50 m.y ago demonstrated the dynamics of geological changes due to the complex plate boundaries and formation from ophiolites of the Philippines Plate and the Indian-Australian Plate.

EXTENSIONAL TECTONIC INVESTIGATION BASED ON GRAVITY AND MAGNETIC DATA ANALYSIS IN THE GULF OF TOMINI, INDONESIA

The enigmatic genesis of Sulawesi Island remains a debate among earth scientists up to the present day. The Northern Arm of Sulawesi is designated as a volcanic province, while the Eastern Arm is identified as an ophiolite zone along with several micro continental fragments. However, the tectonic relationship in the marine area between these two arms is not clearly defined. The existence of isolated volcanic islands, namely the Una-Una and Togian islands increases the complexity of the area. A regional study utilizing gravity and magnetic methods is needed in the Gulf of Tomini, North Sulawesi, Indonesia. Therefore, a comprehensive analysis was conducted, involving 3D inverse modelling and Moho depth estimation based on the Parker-Oldenburg algorithm using 3D Euler deconvolution to obtain the average depth of causative bodies. As a result, the presence of extensional tectonics were revealed and identified as multiple parallel dextral strike-slip faults across the study area. All of these faults show northwest-southeast lineaments consistent with the existing seismic sections. The extensional tectonic mechanism triggers crustal thinning and rifting, leading to the build-up of graben structures such as the Gorontalo, Tomini, and Poso basins. Additionally, it influences volcanic activity around the Togian and Una-Una islands. The major axes of the inferred opening area are oriented in the northeast-southwest direction, perpendicular to the lineaments of these faults. The opening area coincides with the orientation of Lalanga and Togian ridges. Finally, a regional geological structure is proposed across the Gulf of Tomini linking both the Northern and Eastern arms of Sulawesi.

Laterite profile study of highly weathered ultramafic rocks from the southern part of Southeast Sulawesi

This study was carried out in South Konawe Regency, namely in the southern portion of the Southeastern Arm of Sulawesi, with sampling sites made in four different Block areas: (1) Lati Block (Lalembuu-Tinanggea), (2) Torobulu Block, (3) Bangun Jaya Block, and (4) Laonti Block. Determining the profile of laterite deposits created by weathering processes in ultramafic rocks is the goal of this research. The research approach employed is to identify the physical characteristics of their outcrop layering order from top to bottoms of the laterite deposits, such as their color, texture, layer thickness, and mineral composition. In contrast to laterite deposits generally, laterite deposits developed in the South Southeastern Arm of Sulawesi exhibit a unique profile. In particular, the Southeast Sulawesi Arm region’s tectonic activity is closely related to the potency for the development of laterite deposit profiles. The laterite profile types in the research area can be identified by the overburden of each profile, which consists of limestone, sandstone, and a thin layer of coal.

SYNOPSIS OF BEGONIA (BEGONIACEAE) FROM THE NORTHERN ARM OF SULAWESI AND SANGIHE ISLAND, INDONESIA, INCLUDING THREE NEW SPECIES

The Begonia diversity of the northern arm of Sulawesi and the adjacent Sangihe Talaud Islands, Indonesia, is reassessed, and distribution maps, proposed IUCN conservation category categories, and an identification key to 22 recognised species are presented. Three new species, namely Begonia kinhoi, B. pitopangii and B. sojolensis, are described and photographs provided. Newly available material allowed a reassessment of the morphological variability of several species that were originally described from very limited material (Begonia carnosa, B. cuneatifolia, B. gemella, B. hispidissima, B. masarangensis, B. mendumiae and B. strachwitzii), and revised descriptions and photographs of these species are provided. Begonia heteroclinis is reduced to synonomy of B. carnosa, and both names are lectotypified. Additionally, recircumscription and revised synonymy of Begonia rieckei are presented.

Abiogenic gas seepage from serpentinite at Tanjung Api, Tomini Bay, East Sulawesi

Oil and gas seeps are common across the Indonesia region and are usually associated with breached anticlines or faults in Cenozoic or Mesozoic sedimentary basins, where they were generated from biogenic or thermogenic conversion of organic matter in sediments. In contrast, the methane gas at Tanjung Api in East Sulawesi is emerging from an area of ultramafic mantle rocks, which are part of the large East Sulawesi Ophiolite Complex.Tanjung Api is a prominent cape along the South side of Tomini Bay (also called the Gorontalo Basin, along the north shore of the East Arm of Sulawesi). The name means ‘Fire Cape’ and reflects the presence of several burning gas seeps on the beach. This phenomenon must have been active and known for more than 150 years, as the name was already shown on Dutch topographic maps in 1869, and possibly earlier.In this brief review of the enigmatic Tanjung Api gas seeps, we argue that the gas is not a conventional, organic-derived hydrocarbon gas, but an abiogenic (or abiotic), gas, dominated by isotopically anomalous methane and hydrogen, which formed from the serpentinization of ultramafic rocks.

Neogene history of fluvial to shallow marine successions in the Kendari Basin, SE Sulawesi, Indonesia

AbstractCollision between Australia and SE Asia began in Sulawesi, the world's eleventh‐largest island, in the Early Miocene and subsequently Neogene sediments were deposited largely in coastal to shelf environments throughout the island. These sediments have been assigned to the Celebes Molasse, previously considered as a single post‐orogenic unit deposited unconformably on pre‐Neogene sedimentary, metamorphic and ophiolitic rocks. The most complete and extensive sequences of Neogene sediments are in the Kendari Basin, situated at the southern end of the SE Arm of Sulawesi, where an outcrop‐based sedimentological study was undertaken to interpret depositional environments, palaeogeography and stratigraphy. The oldest Neogene sediments are shallow marine carbonates and deltaic siliciclastics of the Bungku Formation. They are unconformably overlain by the Upper Miocene Pandua Formation which consists of sediments deposited in a variety of environments including braided river channels, fluvio‐tidal channels, tidal flats, mouth bar complex and shoreface deposits. A Mio‐Pliocene subaerial unconformity separates the marginal marine serpentinite‐rich sediments of the Pandua Formation from the overlying fluviatile quartz‐rich Langkowala Formation. The sediments of the lower part of the Langkowala Formation include conglomeratic channel fill, while the sediments of the upper part are transgressive deposits decreasing in maximum grain‐size, marked by a reduction in channel/overbank ratio and increasing tidal influence. The transgressive Pliocene Eemoiko Formation is characterised by transgressive lags or onlap shell beds and deposits of a landwards‐backstepping carbonate platform. The improved understanding of the Kendari Basin will aid the interpretation of the sedimentation history of frontier basins surrounding SE Sulawesi, many of which have not yet been drilled.

Tectonic Geomorphic of Sulawesi Island and Its Implication for Future Large Earthquake

This paper analyzes how resource of past and prospective great earthquake on the Central Sulawesi Arm, adhere on topography analysis from several space-based source. To answer the question, we analysis the tectonic geomorphic, stream pattern, exhumed fault, geological mapping and seismicity data. Detailed tectonic geomorphic studies in Sulawesi still lacking due to tectonic and fault obscures. For instance, Palu Koro Fault (PKF) was unpredictable, because the historical seismic records inevitably remain poorly documented and unrecognized fault strand, which was buried beneath abundant Quaternary alluvium subsequently obscured the fault trace. In other hand, the faults have been active during Quaternary must take into account because potentially dangerous, also the inactive faults during instrumental period must be re-evaluated in order to have awareness for large future large earthquake. Surprisingly, recent seismic activity of PKF generate super shear rupture a Mw 7.5 earthquake on 28th September 2018 with average slip 41 mm/year, which over the past two decade quiet from any seismic activity. The seismic potential for large fault is essential, since it has been silent during the instrumental period. Therefore, our motivation in this study to produce detail tectonic geomorphic map of the region in local scale, which is currently not available to prepare better knowledge and awareness for the large future earthquake. We have use Shuttle Radar Topography Mission (SRTM) with resolution ~30m, which run by ArcGIS software to observed tectonic geomorphic evidence of fault system and supplement with structural, geological and bathymetric data’s as ware available to us. We relate this analysis with seismicity data from Centroid Moment Tensor Solution (CMT) to recognize the seismic source. Our results show the tectonic geomorphic of Central Sulawesi Arm due to nature extension of NNW-SSE left-lateral slip curving to WNW-ESE of Palu-Koro Fault (PKF), then transcript to N-S circular normal fault of Poso Fault (PF). The PF indicate replica of PKF curving, where has not been mapped previously. We have mapped 60 major onshore fault systems, 10 faults showed evidence maximal to rapid rate tectonic activity along instrumental periods. Based on our CMT analysis, Sulawesi Island is greatly dominated by oblique fault.

PENENTUAN SUMBER GEMPA LOKAL BERDASARKAN WAKTU TIBA GELOMBANG P DAN S: STUDI KASUS LENGAN UTARA PULAU SULAWESI

Determination of the source of the earthquake has been carried out in the north arm of Sulawesi. The earthquakes analyzed were a local earthquake with a magnitude of more than 5 M. The source of the earthquake is the main variable in earthquake disaster mitigation. Determining the source of the earthquake using the arrival time of the P/S wave. The arrival times of the P/S waves were validated with a Wadati’s chart to test the convergence of the data. Determination of the source of the earthquake was analyzed using HYPOINVERSE. The source of the earthquake obtained has variations in depth and position. Comparison with the catalog shows a significant difference.