Palu-Koro Fault Research Articles

The Palu-Koro Fault Behaviour Monitoring associated with the 2018 Palu Earthquake based on the Multi-temporal PlanetScope and Landsat 8 Satellite Images

The Palu-Koro Fault Behaviour Monitoring associated with the 2018 Palu Earthquake based on the Multi-temporal PlanetScope and Landsat 8 Satellite Images

Technical Study of the Concept of Permanent Housing Relocation around the Palu Koro Fault after the 28 September 2018 Disaster

The earthquake that struck Central Sulawesi on September 28, 2018, had a significant impact on Palu City, Donggala Regency, and Sigi Regency. The impact included a tsunami along the coast of Palu Bay and liquefaction in several areas, leading to extensive damage to infrastructure. As part of the post-disaster recovery efforts, permanent shelters (HUNTAP) are being constructed for the survivors. The purpose of this research is to perform a technical assessment of residential relocation based on risk factors that could lead to future disasters. The method involves descriptive analysis, including the following stages: (1) Reviewing literature from various journals, regulations, technical provisions, and related databases, and (2) identifying variables and criteria that could lead to disasters in areas designated for permanent residential relocation. The research results reveal several influential variables, as follows: (1) Potential for flooding, including: (a) high rainfall, (b) susceptibility to air infiltration, (c) risk of flash floods, (d) erosion of river basins, (e) sedimentation, (f) availability of adequate drainage system facilities; (2) risk of landslides is significantly influenced by: (a) shear angle, (b) pore water pressure, (c) slope gradient; (3) liquefaction indicators include (a) Groundwater level less than 10 meters, (b) sandy soil thickness less than 12 meters underground, (c) increased surface earthquake activity, (d) soil density; (4) tsunami risk is associated with several influential variables: (a) Shallow epicenter with a depth of less than 33 km (b) angle and type of fault, with thrust or thrust faults being the most dominant, (c) distance from the epicenter and location in the middle of the sea, (d) characteristics such as beach shape, open beach morphology, low surface slope, and seabed depth; (5) high current voltage is indicated by the distance and type of voltage capacity; and (6) airplane trajectories are influenced by runway distance and flight path.

Mapping Fault Distribution Using Lineation and Fault Fracture Density Methods in the Palu Basin and Surrounding Areas

Introduction: Research has been carried out with the title "Mapping Fault Distribution Using Lineation and Fault Fracture Density Methods in the Palu Valley and Surrounding Areas" with the aim of determining the direction of fault distribution and analyzing fault density based on lineation data. Methods: This research uses the lineation method with a total of 40 grids. Data processing uses Global Mapper 18, rockwork 17, PCI Geomatica 2014, and Arcgis 10.8 software. Result and Discussion: The results obtained show that the lineation data from the dominant rose diagram has a relatively east-west direction. Areas that have high fault density are in Lindu District, Palolo District, Nokilalaki District, Gumbasa District, Dolo District, Sigi Biromaru District, and Mantikulore District with fault density values of 5,945 - 18,950/km2. Conclusion: The direction of lineation obtained tectonically is influenced by the Palu-Koro fault which tends relatively north-south, the Graben Palolo A and Graben Palolo B faults which trend relatively southeast-northwest, and the Lore Lindu fault zone. Areas with high density are weak zones that are vulnerable to natural disasters and potential ground movements.

Triggered and recurrent slow slip in North Sulawesi, Indonesia

Nearby faults interact with each other through the exchange of stress. However, the extent of fault interaction is poorly understood. In particular, interactions may lead to slow-slip activity, resulting in episodes of transient surface motion. Our study concentrates on Northwest Sulawesi (Indonesia), which hosts two fault zones with potential for major earthquakes and tsunamis: the strike-slip Palu-Koro fault and the Minahassa subduction zone. Thanks to a 20-year-long effort in geodetic monitoring, we are able to identify multiple periods during which surface velocities deviate from their interseismic trend. We use a Bayesian methodology with forward predictions of slip on the two fault interfaces to match the observations following the 2018 Mw7.5 Palu earthquake, and infer that both deep afterslip on the Palu-Koro fault and slow slip on the Minahassa subduction interface have caused the observed transient surface motion. This finding represents the first recording of a slow slip event on the Minahassa subduction interface. We also infer that the subduction interface and the strike-slip fault are likely interacting on a regular basis.

Post liquefaction effect on 1 and 2-dimensional model: a case study of Pasigala raw water transmission structure

Abstract The Liquefaction phenomenon that occurred in Central Sulawesi in September 2018 was triggered by a powerful earthquake that caused extensive destruction and loss of life. Due to its location close to the most active fault in Central Sulawesi, Palu Koro fault, there is still a high probability of recurrence of liquefaction near the area. Ikhsan et al (2023) found that near Sigi regency, certain spots are susceptible to liquefaction occurrence, especially near Maranatha village. This research aims to find the effect after the liquefaction near the Pasigala raw water bridge transmission construction in Sigi Regency if a similar earthquake occurred. It needs to be done because Pasi gala raw water transmission is one of the main raw water supplies to central Sulawesi. Some geotechnical data were carried out in this research such as stratigraphy, SPT, groundwater level, and seismic data. The Post liquefaction analysis was carried out using Idriss and Boulanger (2008) to define one-dimensional settlement potential from the spatial distribution of the liquefaction zone. Numerical models were compared to analyze the settling behavior in a two-dimensional model. The Empirical and Numerical results indicate that the settlement near the abutment’s structure over the 2018 earthquake simulation exceeded the permissible limit of 15 centimeters. This finding may lead to the prediction of damage to the entire structure.

Imaging the Fault Plane Structure of Palu-Koro Fault from Earthquake Data Using Python

Abstract Palu-Koro Fault is one of the active faults located in Sulawesi and positioned in the middle of the Island, dividing the west and east-southeast arms. Its long history of earthquakes provides sufficient focal mechanisms data to be analyzed. This research used seven focal mechanism data of shallow magnitude earthquakes surrounding the pull-apart basin area of the Palu-Koro Fault. The focal mechanism data used is secondary data obtained containing the information needed. This research aims to create a 3D model of the pull-apart basin displaying the geometries of the fault planes and providing a closer look at the fault system surrounding the bounding fault zones. Python script was made to classify the mechanism of each earthquake based on its correlation to the trend of the Palu-Koro Fault. Nodal planes are categorized as whether it is presumed to be the fault plane or the auxiliary plane of the focal mechanism. The result found that not all earthquake data was classified through the assumed parameter set. Only five of seven earthquake data managed to be classified, while the rest showed a different focal mechanism. It is found from the python script created revealed the presence of three fault types: normal fault, normal left lateral oblique fault, and left lateral strike-slip. The 3D fault plane interpolation showed two distinct dipping directions, suggesting their association with the basin’s bounding fault, either the west or the east side. From the gathered information, previous research, and geological interpretation, the earthquake data can be concluded into three fault associations to the bounding fault: synthetic extension fault, antithetic extension fault, and sinistral strike-slip fault.

Identification of Subsurface Structure Causing Liquefaction in Palu City Based on Gravity Anomaly

Abstract Liquefaction in Balaroa and Petobo, Palu City occurred following the September 28 2023 earthquake which was triggered by movement of the Palu-Koro fault. It is necessary to study the existence of local geological factors which may be the cause of liquefaction in these areas. One of the contributing factors could be the existence of small structures as a follow-up to the main structure of the Palu-Koro fault. Using gravity methods at both regional scales for the Palu area and detailed scales in the Balaroa and Petobo areas to identify the presence of subsurface structures. In June 2023, gravity measurements were carried out after the Palu-Donggala earthquake in the Palu City and its surroundings. The measurement results of the gravity anomaly map in the Palu City are in the range of gravity anomaly between -4 – 66 mGals. The Balaroa region is in the gravity anomaly between 19.5 – 34.5 mGals, while Petobo is in the range -2 – 10 mGals. The gravity anomaly map shows the appearance of a structure which is characterized by the contrast of the anomalies which form a lineament which is believed to be a structure. The results of the analysis of gravity anomalies confirm the existence of small structures trending west-east and north-south in the Balaroa and Petobo liquefaction areas which may be one of the causes of liquefaction.

Gravity Modelling Insights into Crustal Structure: Moho Depth and Subsurface Structures in Central Sulawesi

Abstract The present study examines the underlying structures and Moho depth’s geological implications in Central Sulawesi. Comprehending the underlying features of this area is essential for evaluating seismic risks and geological mechanisms. From the World Gravity Map 2012 (WGM 2012), we used a 2D radially-averaged power spectrum analysis of Bouguer gravity anomalies. The Moho depth is around 31 km in the northwest and northeast, with significant fluctuations in the middle and eastern regions. Although the northeastern and northwestern regions have similar depths, the center region has a lower Moho depth. On the other hand, the Palu-Koro Fault limit is marked by the eastern area, which corresponds to the Matano Fault, mirroring the center region. Furthermore, substantial orogenesis inside the Eastern Tokorondo Complex is suggested by Moho depth thinning, especially in the central, eastern, and southern portions. Our research emphasizes Central Sulawesi’s complicated geological structures, marked by variable Moho depth and underlying formations. With implications for earthquake risk assessment and hazard reduction, these insights advance our knowledge of the region’s geological processes.

Frictional Fault Strength Analysis of Palu-Koro and Matano Faults, Sulawesi, Indonesia, from Earthquake Focal Mechanism Data

ABSTRACT Sulawesi’s complex tectonic setting generates active Palu-Koro and Matano faults. Understanding earthquake mechanic is important for mitigation purpose. We performed fault strength analysis by examining its friction, through joint stress inversion and stress magnitude estimation approach, using focal mechanism data from International Seismological Centre bulletin. Friction was analyzed in four segments of the Palu-Koro Fault and two segments of the Matano Fault. Bootstrap and Jack-knife are applied to assess its uncertainty. From north to south, the friction pattern increases at the Palu-Koro Fault segments: Donggala (0.35<μs <0.56) to Palu segment (0.59<μs <0.76); then decreases sequentially: at Saluki (0.49<μs <0.55), Moa segment (0.31< μs <0.35), and further at the Matano Fault segment (Pamsoa-Ballawai) (0.26<μs <0.3). Regarding the 2018 Mw 7.5 Palu earthquake rupture, high friction at the Saluki segment coincides with and indicates its rupture termination. Seismicity records from 1977 to 2011 showed that the largest event occurred at Matano Fault has Mw less than 7.5. Low friction observed at Matano Fault correlates with small magnitude events and low fault strength.

A new moment tensor catalogue of light to moderate earthquakes in Palu-Koro and Matano faults, Sulawesi, based on the regional network in Indonesia: Fault analysis and insight

Starting from 2009, substantial improvements in the regional seismic network operating in Sulawesi, as part of the Meteorological, Climatological, and Geophysical Agency (BMKG) station deployment, allowed us to determine earthquake mechanism for 140 shallow (5–60 km) light to moderate size (3.8 ≤ Mw ≤ 6.1) earthquakes between 2009 and 2018 along the Palu-Koro and Matano faults, through moment tensor inversion. Ten (10) out of the 140 solutions obtained in this study were found in the International Seismological Centre Bulletin and used as validation. The double-couple mechanism of the best solutions (variance reduction ≥0.4 and condition number ≤ 7.5) is further used to analyze the Palu-Koro and Matano segments. We observed that the Donggala segment of the Palu-Koro fault shows variable earthquake mechanism types. Whereas the two subsequent segments, the Palu and Saluki segments, show predominate oblique strike-slip with normal and reverse mechanisms. The Matano fault is characterized by strike-slip mechanisms, with normal mechanisms also observed. The normal mechanisms depict the pull-apart system in the Matano segment, manifested as Matano Lake. The results of this work improve our understanding of regional tectonics.

IDENTIFICATION OF ELECTROMAGNETIC ULTRA LOW FREQUENCY (ULF) SIGNAL ANOMALIES AS PRECURSORS OF A MAGNITUDE 5 EARTHQUAKE IN THE SULAWESI REGION

Sulawesi is situated at the intersection of three tectonic plates the Indo-Australian, Eurasian, and Philippine plates. The Palu Koro fault is one of the primary causes of seismic activity in the Sulawesi region, making it vulnerable to earthquakes on this Island. As an initial step in disaster mitigation, the information provided is useful in determining the initial signs before the occurrence of an earthquake, it is necessary to identify Ultra Low Frequency (ULF) Signal Anomalies as earthquake precursors. The methods employed are those of power spectrum density (PSD) and single-station transfer function (SSTF). The analysis of anomalies suspected of being precursors to 5 earthquake events revealed that in the February 27, 2023 earthquake, the anomaly appeared twice with a lead time of 17 days. In the February 28, 2023 earthquake, the anomaly appeared twice. In the March 7, 2023 earthquake, the anomaly appeared 3 times with a lead time of 20 days. The March 28, 2023 earthquake had 6 anomalies with a lead time of 24 days. The April 6, 2023 earthquake had 5 anomalies with a lead time of 29 days. anomalies were detected with lead times ranging from 17 to 30 days. The anomaly source azimuth direction was also determined.

Analysis of Existence and Faults Impact on Geological Disasters Using GGMPlus Data

The existence of faults can trigger various geological natural disasters because faults will react when an earthquake occurs and volcanic activity occurs, causing effects in the form of landslides, subsidence, ground movements, and other geological disasters. This research aims to analyze the existence and impact of local faults on geological disasters around the research location using GGMPlus data. A derivative filter is used to get FHD and SVD maps based on the gravity anomaly map. Fault analysis was carried out using a graph from the FHD and SVD map incisions, which were then correlated with each other. The incision graph of the meeting point between the maximum FHD value and the zero SVD value will be interpreted as a fault structure. The results show that there were several fault indication points; these points were then drawn straight lines to get the lineaments of the faults. The fault lineaments with the location of the landslide and subsidence events are correlated so that it becomes evident that the subsidence and landslide disaster in the Brau Hamlet, Batu City, area can be associated with local faults. Based on several previous research on determining faults in coastal areas, it is known that the areas crossed by the Palu-Koro fault have experienced many disasters, such as landslides, land movement and liquefaction. The existence of local faults in an area can increase the impact of damage when natural disasters such as earthquakes and landslides occur.

Assessing soil vulnerability in Petobo post-liquefaction zone, Palu, Central Sulawesi: A microzonation study utilizing microtremor measurements

On September 28, 2018, a 7.5 Richter magnitude earthquake struck the Palu City neighborhood of Petobo. The tectonic activity along the Palu-Koro fault generated this earthquake, which resulted in soil liquefaction. The purpose of this study is to use microtremor measurements at 33 distinct places to investigate the properties of the soil layer after liquefaction. The obtained data was then evaluated utilizing Horizontal to Vertical Spectral Ratio (HVSR) methodologies such as Ground Shear Strength (GSS), amplification factor, and vulnerability index to determine the soil layer's properties and susceptibility. The dominant frequency ranges from 0.19 to 4.75 Hz, while the dominant period ranges from 0.21 to 5.17 seconds, according to the measurement results. According to these measurements, the silt layer varies between 5 and 30 m. GSS values in the 10-4 to 10-2 range indicate that soil cracking, subsidence, liquefaction, landslides, and compaction are likely. The soil vulnerability and amplification index values range from 2.36 to 4.37, respectively. These values show the potential level of danger, which might be low, medium, high, or extremely high. Peak ground acceleration varied from 299.52 to 301.52 gals, suggesting high to extremely high danger levels. The microzonation map created for this study is considered to be a useful resource for training disaster mitigation approaches and facilitating infrastructure development planning in the region.

Palu-Koro Fault on Social Media: Mixed Approach Study of Disaster Information Spread and the Potential of Geotourism Promotion

This article discusses the role of influencers, social media, and information spread in promoting the geotourism of the Palu-Koro Fault. As one of the governmental bodies responsible for geotourism, the Central Sulawesi Provincial Tourism and Creative Economy Office is trying to introduce these relatively new geotourism sites. One of the efforts is to make full use of social media. Influencers are collaborated with not only to introduce geotourism but also to build branding. Geotourism is one of the many topics brought up by social media users regarding the post-disaster recovery efforts in Pasigala. Thus, in this study, we applied a mixed-method analysis by comparing the analysis of the data collected from Twitter using a descriptive quantitative approach utilising structural and actor-based social network analysis and in-depth interview data with key informants from the Central Sulawesi Provincial Tourism and Creative Economy Office staffs and three influencers in collaboration using descriptive qualitative-case study approach utilising narrative analysis. The results showed that most Twitter users sought prominent actors, such as influencers and government officials, for information in time and after the disaster struck. While the three disasters are the most heavily discussed, post-disaster programs and plans are also prominent, including geotourism. The Central Sulawesi Provincial Tourism and Creative Economy Office collaborated with the influencers due to their ability and potential to spread information fast and wide to their followers. The message is formed to promote the newly formed geotourism sites, educate people, and build positive views of the impacted sites. Keywords: Geotourism, Palu-Koro, social media, information, social network analysis.

Local Government Resonance on Disaster Potential Issues

Ring of fire that surround Indonesia from east to the west made this country become potential vulnerable to various types of natural disasters, Morowali is a district located in central sulawesi province that one of a disaster-prone area. It is traversed by the Matano fault which connected to Palu Koro fault which is a fault with approximately 8 mm active movement per year. This study aims to see how far the local government of Morowali responds to the issue of potential disasters, consider that Morowali district is one of the areas designated by the state government as a special economic zone. This study using an exploratory case study that does not see phenomena only from problems but also in the form of social activities, groups, and organization. Niklas Luhmann's concept of resonance is the main reference in describes the interconnection between systems and the environment. Research data obtained using in-depth interviews, focus group discussions, and field observations. The informants in this study were executive and legislative board. The results show that the executive and legislative response to the issue of potential natural disasters shows the resonant capacity of two functional systems politics and economics are weak, which shows that the government's system should encourage the concept of proactive adaptation to strengthen its response to the existing potential disasters and create security for the Morowali community.

Dynamic analysis of geophysical characteristics of Una-Una Volcanic Island, Sulawesi, Indonesia

The Una-Una Volcanic Island is an active and isolated island, and its deep structure and dynamic causal mechanism have yet to be fully understood. The island is situated in Tomini Bay, between the north and east arms of Sulawesi Island in Indonesia. Around 5 Ma, the Sula Islands collided with the east arm of Sulawesi Island, which caused the subduction and retreat of the North Sulawesi Trench. Additionally, a sinistral strike-slip of roughly 4 cm/a initiated at the Palu-Koro fault on the western side of Sulawesi Island, ultimately leading to the formation of the isolated Una-Una Volcanic Island in Tomini Bay. Here, we utilized gravity, seismic, magnetic, and heat flow data to calculate the geophysical characteristics of three-dimensional temperature, velocity, and viscosity of the northern Sulawesi region. The results of our research showed that the crust in the northern region of Sulawesi Island is primarily characterized by brittle deformation. However, the presence of a southward-inclined weak layer in the crust, which resulted from the subduction of the North Sulawesi Trench, caused the region between the terrain and the Moho surface to exhibit a combination of brittle and ductile deformation. The weak zone in the crust in the northern region of Sulawesi Island is the primary controlling factor for the development of sinistral strike-slip. The uplift of the crustal weak area below the Una-Una Volcanic Island was caused by the southward subduction of the North Sulawesi Trench and the northward push of the Banggai-Sula microblock, ultimately leading to the formation of the Una-Una Volcanic Island in Tomini Bay.

Indonesian “tsunami-generation” in a nutshell: systematic literature review

Publications related to tsunami-generation phase hold 42.8% of all the publications over all tsunami hazard literatures in Indonesia. Corroborating the fact, tsunami-generation studies are also vital in determining the type of propagation and inundation that may appear in the surrounding coastal regions, which in practice, can also help determining disaster management specifics and risk reduction activities. A literature review regarding tsunami-generation has been done for those purpose by using our CARI! Knowledge Engine, which includes collections of both International and Indonesian journals within the scope of Indonesian locus context. This study unpacks publication trend, the most influential articles, top contributing journals, top main authors, top institutions, and dominant countries as well as the science mapping of tsunami-generation subjects. To gain deeper understanding, we also develop tsunami-generation research framework within the basis of tsunami generation force, time occurrence, monitoring, and measurement approach, as well as hazard analysis approach. From the review, an interesting peak of tsunami-generation publications has been shown in 2020 (39 publications), following the occurrence of several Indonesian major tsunamis in the previous decade and the globally impacting Aceh Tsunami (or the Indian Ocean Earthquake and Tsunami) in 2004. Among all the publications of tsunami-generation force, tsunamigenic earthquake has become the most studied topic (67.7% of all publications), while the most discussed atypical sources mainly come from volcanic eruption (46.67% of all atypical literatures) and submarine landslide (33.33% of all atypical literatures). In terms of tsunami-generation source, it is found that the Sunda Megathrust has been the most-discussed location, which is mentioned within 39 publications, followed by the Palu-Koro Fault with 18 publications and the Krakatau Volcano by 16 publications. Apart from the notice of significant difference between research of historical tsunami and paleotsunami (120:5 publications), some gaps also can be found when discussing the meteotsunami-generation mechanism in Indonesia and the Global Navigation Satellite System’s Total Electron Content (GNSS-TEC) method, which, although proven beneficial for the development of tsunami early warning system, accuracy is still the main issue in capturing tsunami signals and positioning actual source location of tsunami. These were some highlighted limitations that arise in our process to understand tsunami-generation mechanisms and the exploitations of the knowledge. Therefore, future studies specifically within these areas are further encouraged.

Evaluation of Liquefaction Potential Index in the Educational Infrastructure Reconstruction Project at the University of Tadulako, Palu City, Central Sulawesi

On September 28, 2018, The Palu-Koro fault triggered an earthquake of Mw 7.5. at a depth of 20 km and 72 km northeast of Palu City. As a result, the University of Tadulako suffered significant damage post this earthquake. The Ministry of Public Works and Housing was assigned to reconstruct this location, which was located near the epicentre, and there are alluvium deposits of the Holocene age with loose sand soil and shallow groundwater levels on-site. Based on the Indonesian Seismic Code SNI 1726:2019, it is necessary to propose liquefaction potential and mitigation for building planning. The study aims to calculate the Safety Factor (S.F.) against liquefaction using a simplified procedure by Seed-Idriss and developed methods by Idriss-Boulanger. The S.F. was used as an input to determine the Liquefaction Potential Index (LPI) by Iwasaki et al. The study showed different categories of LPI values. The highest LPI value was found at BH-05, with a very high liquefaction potential. The soil depths susceptible to liquefaction are up to 9 meters. Application of deep foundation penetrating liquefiable soil layer is recommended as the mitigation. It is necessary to conduct further studies on the deep foundation analysis to be applied to this location.

A Preliminary Tomography Inversion Study on the Palu Koro Fault, Central Sulawesi Using BMKG Seismic Network

The Palu Koro Fault, which frequently causes solid and destructive earthquakes, is the most exciting aspect of Central Sulawesi’s tectonics. We used local earthquake data from the area in this preliminary study. Our preliminary investigation entails analyzing local seismic data and estimating the velocity structure and hypocenter location using a tomographic approach that employs P-wave arrival times from the Agency for Meteorology, Climatology, and Geophysics earthquake observation network from 2010 to 2019. We use a 1-D initial velocity structural model in this tomographic inversion method, and the results are evaluated using the checkerboard test, derivative weight sum, and ray hit count. To the west and east of the Palu Koro Fault area, preliminary tomographic inversion results show a relatively high seismic velocity. These areas are interpreted as West Sulawesi Mandala and East Sulawesi Mandala Poso Fault and Wekuli Fault. The low-velocity anomaly is found near the Palu Koro Fault. Because of the high-speed thrusting, the relocated hypocenters also clustered around the Palu Koro Fault area. In the following activity, we will determine the speed structure of the S wave, which is expected to provide better geological information in the interpretation.

The Effects of Palu-Koro Fault on Predicting Ground Motion for Estimating Liquefaction-Induced Settlement of the Educational Infrastructure Reconstruction Project at the University of Tadulako

The University of Tadulako suffered significant damage after a tectonic earthquake with a magnitude of M 7.5 with a depth of 20 km that occurred on September 28, 2018. This incident happened because of its location very close to the Palu-Koro fault. The Ministry of Public Works and Public Housing was assigned to reconstruct damaged educational infrastructure there. Seismic hazard analysis was needed to prepare reconstruction development projects and mitigation efforts. Many studies are related to predicting ground motion due to seismic fault activity, one of which is the attenuation NGA West 2 models. This study aims to determine the relationship between fault effects and ground motion to estimate liquefaction-induced settlement at this project. The results show that the relationship between the fault effects and ground motion affects various PGA values. PGA value resulting from the CY14 model was used to estimate settlement because it considers the worst condition aspect, where the most significant settlement occurred at the drill point DP-05 of 10.234 cm. This settlement can happen because the liquefied soil layer at the drill point was quite deep compared to other drill points.