Search

In 2022, four earthquakes with MS ≥6.0 including the Menyuan MS 6.9 and Luding MS 6.8 earthquakes occurred in the NorthSouth Seismic Zone (NSSZ), which demonstrated high and strong seismicity. Pattern Informatics (PI) method, as an effective long and medium term earthquake forecasting method, has been applied to the strong earthquake forecasting in Chinese mainland and results have shown the positive performance. The earthquake catalog with magnitude above MS 3.0 since 1970 provided by China Earthquake Networks Center was employed in this study and the Receiver Operating Characteristic (ROC) method was applied to test the forecasting efficiency of the PI method in each selected region related to the North-South Seismic Zone systematically. Based on this, we selected the area with the best ROC testing result and analyzed the evolution process of the PI hotspot map reflecting the small seismic activity pattern prior to the Menyuan MS 6.9 and Luding MS 6.8 earthquakes. A “forward” forecast for the area was carried out to assess seismic risk. The study shows the following. 1) PI forecasting has higher forecasting efficiency in the selected study region where the difference of seismicity in any place of the region is smaller. 2) In areas with smaller differences of seismicity, the activity pattern of small earthquakes prior to the Menyuan MS 6.9 and Luding MS 6.8 earthquakes can be obtained by analyzing the spatio-temporal evolution process of the PI hotspot map. 3) The hotspot evolution in and around the southern Tazang fault in the study area is similar to that prior to the strong earthquakes, which suggests the possible seismic hazard in the future. This study could provide some ideas to the seismic hazard assessment in other regions with high seismicity, such as Japan, California, Turkey, and Indonesia. [ABSTRACT FROM AUTHOR]

Traces of past landslides were found on the seabed of Palabuhanratu Bay, West Java. This landslide is thought to have generated a tsunami, but has never been investigated before. This bay is located around the western part of the Cimandiri Fault which is an active horizontal fault with a length of 100 km. Therefore, it is necessary to study the potential impact of a tsunami in the Palabuhanratu Bay area caused by a combination of local earthquakes and underwater landslides around the bay. Evidence of past landslides was revealed through side-scan sonar data from the underwater research vessel Baruna Jaya IV in Palabuhanratu Bay, Indonesia, in 2020. The data from this survey provides evidence of debris flows (historical landslide data) at the survey site. We simulated 29 tsunami scenarios from combined landslide earthquake sources by solving shallow water nonlinear equations numerically. Tsunami sources from earthquakes are classified into three types, e.g., land faults, sea faults, and combinations of land and sea faults. While the source of the tsunami from the landslide is divided by volume. Combination of the earthquake magnitudes range from M6.80 to M7.85, and the landslide volume ranged from 3.06 × 105 m3 to 2.5 × 108 m3. This study concludes that in our scenario, the M8.12 type T7 earthquake generates the largest tsunami in the study area, followed by the T6L5 scenario with M7.85 from the Cimandiri Fault and landslide with a total volume of 2.5 × 108 m3. [ABSTRACT FROM AUTHOR]

Based on the methodology for studying variations in the properties of small-scale probability density fluctuations when measuring the X-component of the magnetic field, short-term precursors were identified for two earthquakes with magnitudes 7.3 and 6.6 that occurred in the Indonesia region on December 14, 2021, and January 14, 2022, respectively. In both cases, the applied approach made it possible to identify an ensemble of these precursors over an interval of the order of one day to one hour before the indicated events. For the earthquakes under consideration, phenomena of simultaneous or quasi-simultaneous occurrence of groups of precursors were discovered, and time points were identified that could correspond to critical phenomena during the process of "final preparation" of the earthquake. [ABSTRACT FROM AUTHOR]

Destructive earthquakes are frequently related to inland active faults. In recent years, a significant number of shallow earthquakes with low magnitude have occurred in southern Garut, West Java, Indonesia. Two earthquakes, with magnitudes of M4.2 and M3.9 in 2016 and 2017, respectively, have caused significant damage and were interpreted as indications of an active fault. We used publicly available gravity data to infer the subsurface structure that may be related to recent seismic activity. We used spectral analysis and filtering techniques for the regional-residual anomaly separation and anomaly enhancement to show the basin structure in the study area. 3D gravity inversion modelling was performed to obtain the subsurface density distribution. The result indicates the sedimentary layers with a density of 2.4 to 2.5 gr/cm³ with an underlying basement with a density of 2.65 gr/cm3 . An intra-basin basement high with an NE-SW trend divides the basin into two sub-basins. This local basement high can be associated with a magmatic intrusion body and a series of young volcanic bodies located at the northeastern end of the basin. Our results emphasize a possible strong interaction between the tectonic and magmatic activities in this region. [ABSTRACT FROM AUTHOR]

We conducted a study on the Aceh Fault, an active right-lateral strike-slip fault in northern Sumatra, Indonesia. Despite its seismic hazard potential, the slip characteristics of this fault are not well-understood. Using a combination of remote sensing and field methods, we mapped the distribution of displacement recorded by offset channels along the fault. Our goal is to identify evidence of past surface rupture, characterize their tectonic geomorphology setting, and assess their potentials as slip-rate and paleoseismic sites. The documented right-lateral displacements of channels and ridges from 35 observation points are mostly in the order of magnitude of hundreds of meters, with only a few sites exhibiting meter-scale measurable offsets. Our results provide important first-order data that can be used to locate sites suitable for paleoseismic trenching or offset investigations. This information will support the development of a maximum magnitude and earthquake recurrence model of the fault, which are crucial for seismic hazard analysis in the region. [ABSTRACT FROM AUTHOR]

Peak Ground Acceleration (PGA) is a crucial factor in infrastructure planning, particularly in the context of constructing the Jogja-Bawen Toll Road in Magelang Regency. However, there is a lack of comprehensive research on the optimal PGA value for this region. This research addressed this gap by analyzing two significant earthquake scenarios, namely the Bantul and Yogyakarta earthquakes, with magnitudes of 6.3 Mw and 7.44 Mw, respectively. Three methods were employed for this analysis, namely the Indonesian seismic code, Kanno (2006), and Fukushima (1990) attenuations, as well as microtremor measurements. The PGA value generated by the seismic code ranges from 0.348-0.380g. For the 6.3 Mw earthquake scenario, the Kanno attenuation results in a PGA range of 0.115-0.181g, the Fukushima attenuation yielded 0.082-0.114g, and the microtremor measurements indicated 0.036-0.092g. In the case of the 7.44 Mw earthquake scenario, the Kanno attenuation generated a PGA range of 0.202-0.265g, the Fukushima attenuation produced 0.052g-0.062g, and the microtremor measurements indicated 0.036g-0.088g. The result showed that the PGA value derived from the seismic code is relatively higher because it considered various earthquake models and magnitudes. Meanwhile, the PGA value obtained from microtremor measurements was smaller due to the consideration of site class and site-specific amplification factors at the study site. [ABSTRACT FROM AUTHOR]

Lake Toba Crater, specifically Samosir Island, Indonesia, is a caldera formed by the supervolcano eruption of Mount Toba. Furthermore, the region is susceptible to active earthquakes due to the presence of the Sumatran fault. Along the coastline, the soil is predominantly sandy, with a high groundwater level. These factors, namely earthquake and soil conditions, are reported to be the major triggering factors for a phenomenon known as liquefaction. According to the Indonesian Liquefaction Vulnerability Zone, Samosir Island is situated in a vulnerable area with medium potential. Therefore, this study aims to evaluate the liquefaction potential in Lake Toba Crater by taking a study case in the Culinary Building. Due to the SF site class of the study location, Site-Specific Response Analysis (SSRA) was required based on the Indonesian National Standard. A non-linear SSRA was used to determine the seismic wave propagation with DEEPSOIL v7. The analysis considered an earthquake exceedance probability of 2% in 50 years. The input parameters for the ground motion were obtained from the modification of 12 pairs of recorded data. The Peak Ground Acceleration value for each depth was generated from SSRA and used for liquefaction potential evaluation. This study used empirical methods, as well as two scenarios, namely maximum and frequent earthquakes with magnitudes of 6.4 Mw and 5.6 Mw, respectively. Based on the results, the area had liquefaction potential at 6-20 meters below the surface. The vulnerability level, as assessed using LPI value, was found to be very high, ranging from 25.71 to 56.51. [ABSTRACT FROM AUTHOR]

Copyright of Progress in Earthquake Sciences is the property of China Earthquake Administration, Institute of Geophysics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Earthquakes are one of nature's most devastating disasters. Earthquake prediction is critical in seismology since its success can save lives, property, and infrastructure. Numerous technologies have been proposed to address this issue, including mathematical analysis, artificial intelligence, and machine learning algorithms. Unfortunately, due to earthquakes' dynamic and spontaneous nature, they frequently fail to provide positive results. The study uses deep learning techniques to predict the magnitude of an impending earthquake using eight mathematically calculated seismic indicators derived from Japan, Indonesia, and the Hindu-Kush Karakoram Himalayan (HKKH) region's earthquake catalogs. Three deep learning techniques, including Long Short-Term Memory (LSTM), Bi-directional Long Short-Term Memory (Bi-LSTM), and self-attention-based transformer, have been implemented to model the associations between calculated seismic indicators and potential earthquake incidents. These models have been evaluated with well-known matrices such as the Mean Absolute Error (MAE), Mean Squared Error (MSE), log-cosh loss, and Mean Squared Logarithmic Error (MSLE). The value of these cost functions converges to a small number for all models, indicating that these models effectively predict earthquake magnitudes. When these models were fed with an unknown test dataset from Japan, the LSTM model performed best with the least deviation metrics (MAE = 0.060, MSE = 0.006, log cosh = 0.042 and MSLE = 0.003). Similarly, the Bi-LSTM model delivered the ideal result for the Indonesia earthquake catalog (MAE = 0.073, MSE = 0.009, log cosh = 0.016, and MSLE = 0.009), while the transformer model produced the optimal result for the HKKH region (MAE = 0.062, MSE = 0.006, log cosh = 0.043, and MSLE = 0.003). Predicting earthquake magnitude at various locations using these methodologies produces significant and positive results for magnitudes ranging from 3.5 M to 6.0 M, paving the way for the ultimate robust prediction mechanism, that has not yet been developed. [ABSTRACT FROM AUTHOR]

A fault called as Lembang Fault is known as one of the most potential faults in West Java of Indonesia that could trigger earthquakes with magnitude up to Mw 7.0, especially in Bandung Region. This study presents analysis of ground response of Bandung Regency subsoils due to predicted earthquake triggered by Lembang Fault, West Java Province, Indonesia. Site investigation is conducted in the study area. The ground motion analysis is conducted to predict potential ground motion that could happen in the study area. The spectral matching method is employed to generate ground motion in the study area. Furthermore, one-dimensional seismic ground response analysis is performed to observe site response during earthquake. The results show that several sites could undergo amplification and de-amplification. If a Mw 7.0 earthquake happens, the damage intensity level varied from VIII to X could happen. The results also indicate that spectral acceleration at ground surface tends to be critical at long period. Therefore, the implementation of seismic design code for earthquake resistance design should be concerned in the study area. In general, the result of this study could deliver a recommendation to local government to consider earthquake in the study area. [ABSTRACT FROM AUTHOR]

Indonesia is located at the Pacific Ring of Fire and the meeting place of the world's four tectonic plates, which makes Indonesia to have a high tectonic activity and to be prone to earthquakes. Currently, early earthquake detection service in Indonesia is based on seismometers network. However, seismometer instruments that observe seismic waveforms might become saturated, and as such may lead to incorrect earthquake magnitude detection at an early stage. Therefore, a new approach is needed to detect earthquake coseismic information. Global Navigation Satellite System (GNSS) is a good instrument to measure the surface displacement due to an earthquake. However, previous studies in Indonesia still predominantly used daily solution data. To carry out early detection, it is not possible to use daily solutions. Therefore it is needed to use the data with a higher frequency solution than the daily solution. In this study, we used 30-second sampling rate data available from Indonesian Continuously Operating Reference Station (Ina-CORS) and Sumatran GPS Array (SuGAr). We will see how the 30-second GNSS data responds to earthquakes to estimate the value of coseismic displacement compared to daily solution data. The estimated value of this coseismic displacement can be used for earthquake early detection. [ABSTRACT FROM AUTHOR]

A comparison on the influence of different moment magnitude pools on magnitude homogenization regressions was presented. The control moment magnitude pool is composed of earthquake records from GCMT. One version of expanding this base is to add earthquakes with a moment magnitude recorded by seismological agencies related to GCMT. Another approach to expanding the base is to add earthquakes from seismological agencies and projects that show a significant statistical correlation to GCMT via hypothesis testing. These moment magnitude pools were developed for Indonesia and South Korea. Magnitude homogenization was conducted by performing linear least squares regressions between the three moment magnitude pools and commonly used magnitude types from international seismological agencies ISC and NEIC. Magnitude homogenization regressions were also conducted on local Indonesian and South Korean agencies, DJA and KMA, respectively, with their various magnitude types. Most of the moment magnitude pools involving DJA and virtually all South Korean-related agencies ended up being identical, primarily due to the local magnitude types available for DJA, and the low number of earthquakes recorded for South Korea. A majority of the regression parameters for Indonesia and South Korea were statistically similar for surface and body wave magnitude types. [ABSTRACT FROM AUTHOR]

The rapid estimation of the magnitude of an earthquake is an essential part of an earthquake early warning system (EEWS), which is used to respond to earthquake shaking and the possible arrival of a tsunami. This research is the first in Indonesia to use Global Navigation Satellite System (GNSS) as part of an EEWS. Three high-rate GNSS datasets were processed using the precise point positioning post-processing method, which resulted in a peak ground displacement (PGD) and peak ground velocity (PGV) value due to the Lombok earthquake on August 5, 2018. The results showed that the magnitude of the PGD from the station closest to the earthquake source (KDOO) was Mw 6.6 within eight seconds of the original time, while that at the farthest location (CMAT) reached Mw 6.9 within 18 seconds of the original time. At the CMAT station, we also estimated the magnitude using PGV, which showed results consistent with the PGD data. These results confirm the potential use of the PGD and PGV data obtained from high-rate GNSS to estimate earthquake magnitudes rapidly as part of an EEWS. [ABSTRACT FROM AUTHOR]

Copyright of Földrajzi Közlemények is the property of Magyar Foldrajzi Tarsasag and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Recent borehole seismic deployments conducted along the Baribis Fault in northwestern Java reveal that it may be active. In this study, we exploit these data to locate proximal earthquakes using a relative relocation technique, estimate their moment magnitudes using a spectral fitting method and compute their focal mechanisms via waveform inversion. We observe that seismicity in the eastern part of the fault is significantly higher than in the west, where a previous GPS study of the region south of Jakarta demonstrated the existence of high compression rates. These observations imply that the western Baribis Fault is locked, and that neighbouring areas, including southern Jakarta and its surroundings, may be highly vulnerable to future sizeable earthquakes when accumulated elastic strain energy is eventually released during fault rupture. Significantly, the current generation of Indonesia's national hazard maps have not considered seismicity along the Baribis Fault. Our new results therefore call for an urgent reappraisal of the seismic hazard in northwestern Java that carefully takes into account the Baribis Fault and its earthquake potential, particularly in light of its proximity to Jakarta, a megacity that lies at the heart of one of the most densely populated islands in the world. [ABSTRACT FROM AUTHOR]

Earthquake size can be estimated using magnitude-rupture area scaling developed from modelled fault dimensions and measured moment magnitudes. In this study, a measure of a fault plane geometry was provided by rupture area A and the size scaled with moment magnitude Mw. Using global earthquakes datasets containing 90 events with varying magnitudes 4.45 = Mw = 9.20 during years of 1960-2015, we classified the data into separate strike-slip, dip-slip (normal and reverse) and subduction-zone earthquakes. The study aims to search for reliable scaling used for magnitude prediction of earthquakes around the globe for each type of source mechanism. We found from the Mw-A scaling proposed in this study that the magnitude for subduction events was likely to saturate to a maximum value possible Mw? 9.3 at rupture areas much larger than those for strike-slips and dip-slips. This suggests that rocks in the subduction-zone are able to accumulate high stress, implying large seismic energy release via strong ground motion when an earthquake occurs at the plate boundary. Taking into account cases under consideration that included intraplate-fault and subduction processes covering a wide range of magnitudes from moderate to large sizes, the results are relevant to Indonesian tectonic settings, where active crustal faults have been recently found throughout the country and in particular a future megathrust subductionzone earthquake of Mw ~ 9.0 is possible to occur off the south coasts of Java Island, the most densely populated island in Indonesia. These potential seismic threats call for increasing awareness of disaster preparedness, particularly for local community in regions with a high level of vulnerability to tsunami and earthquake disasters. Therefore, a reliable earthquake early warning is of primary importance, which is best integrated into an existing tsunami early warning for maximum security from future seismic hazards. [ABSTRACT FROM AUTHOR]

Introduction: Disasters can happen anytime, anywhere and can affect anyone. Geographically, Indonesia is located at the confluence of three plates world tectonics, namely the Australasia plate, the Pacific plate, the Eurasian plate and Philippines. This causes Indonesia to be geologically vulnerable and is one of the parts of the world that has a complex seismonic system with a fairly high frequency of earthquakes. The potential for earthquakes, both on land and at sea, is very high. Earthquakes with a magnitude of 6-9 Ms are common. The potential for physical and economic damage and losses due to disasters, the highest is for the threat of an earthquake. In general, the main factor is the number of fatalities, damage, and losses incurred arising from the disaster is the lack of understanding and awareness of the community towards disaster risk in the region. This results in awareness vigilance, and preparedness in dealing with disasters are still very not enough. The purpose of the study was to determine the level of community preparedness in dealing with the tsunami. Methods: Descriptive research design used was survey method. The research population was 980 households in Kunjir and Waymuli villages, with 284 samples were taken by cluster random sampling. The instrument was based on LIPI-NESCO/ISDR 2006. Data were processed with SPPS 20 to obtain a frequency distribution Preparedness level community. Results: The results showed that the level of community preparedness from the aspect of knowledge and attitudes, early warning system, and resource mobilization were mostly in the good category, while the planning aspect in dealing with disasters was mostly in the sufficient level. It is concluded that the level of community preparedness is good. Conclusion: The level of community preparedness is in the good category. The research recommendation is that the community should get assistance in planning for the tsunami disaster to reduce the number of victims in the event of another tsunami. [ABSTRACT FROM AUTHOR]

The Sulawesi earthquake with a moment magnitude of Mw 7.5 struck the Central Sulawesi region of the Sulawesi Island, Indonesia, on September 28, 2018. The epicenter of the earthquake was located in the mountainous region of Donggala Regency, in the neck of the Minahasa Peninsula in the Central Sulawesi Province of Indonesia. Although the epicenter was located in Donggala Regency, the greatest devastating effects were observed about 70 km south of the epicenter in the Palu Valley. The event was the first of its kind to cause large-scale flowslides simultaneously at four key locations such as Balaroa, Petobo, Jono Oge, and Sibalaya with extensive ground displacements ranging from several hundred meters to more than 1 km. This article reviews the field observations of geotechnical failures and infrastructure damage caused by liquefaction resulting from the shallow strike-slip earthquake at Palu City, Donggala Regency, and Sigi Regency. A geo-spatial analysis was performed on data collected from aerial drone imagery, along with portable dynamic cone penetration testing (PDCPT) in the field. The investigation revealed a highly stratified ground with alternating soil layers of varying permeability and very low bearing resistance at shallow depths. The investigation also helped in assessing the extent of damage caused by geotechnical failure to the residential infrastructures, irrigation structures, and roads. [ABSTRACT FROM AUTHOR]

Bengkulu City is one of cities in Indonesia, which is located on the west coastline of Sumatra. Within last two decades, Bengkulu City had undergone at least two large earthquakes with magnitudes ≥ Mw 7.0. This paper presents a study of deterministic seismic hazard for Bengkulu City. The hazard analysis is initiated by determining the controlling earthquake. Site investigation results are also studied for seismic ground response analysis. Analysis is performed by propagating seismic wave to investigate seismic behaviour during earthquake. Three parameters including peak ground acceleration, spectral acceleration at 0.2 s (SA at 0.2 s), and spectral acceleration at 1 s (SA at 1 s) are analysed to generate seismic hazard maps. In general, this study could help people to understand seismic hazard in Bengkulu City. The results also could recommend local engineers to consider earthquake in structural design and spatial plan in Bengkulu City. [ABSTRACT FROM AUTHOR]

Ease of accessing and using earthquake and tsunami early warning applications is a priority in this study. It is related to the more time the community prepares for disaster mitigation. The purpose of this research is to produce an Android-based earthquake and tsunami early warning application. The availability of this fast android-based earthquake and tsunami early warning application can help in quicker and more reliable earthquake and tsunami early warning for short distances to areas that have the potential to impact a tsunami. The research method used in this research is the ADDIE development method (Analysis, Design, Development, Implementation, and Evaluation. In the first year, the focus of the development of the Rapid Tsunami Early Warning Application about 4 minutes after O.T. Our previous research results, which have supported many events this application will make it easier for us to complete the prototype target. The prototype of the Android-based earthquake and Tsunami, early warning application, has been tested in real-time at the Faculty of Mathematics and Natural Sciences, Surabaya State University, Indonesia. The results of the trial have shown the eligibility requirements. [ABSTRACT FROM AUTHOR]

Central Sulawesi has very complex tectonic conditions, and therefore the earthquake hazard of the region needs to be carefully examined. One of the required components to develop such examination is regional ground motion prediction equations. This study describes the development of GMPEs for Central Sulawesi based on broadband velocitymeter and strong motion accelerations recorded by instruments managed by Indonesia geophysical authority temporarily since year 2015 and 2017. The accuracy of the resulting equations is examined further by performing the seismicity declustering processes using the Reasenberg method; the declustering process is to separate mainshock events from foreshock and or aftershock events. Note that, as the site class of the instrument locations is SD, the resulting GMPEs are only for SD sites. The resulting expected geometric mean peak ground acceleration from GMPE for all shocks (dependent seismicity) is similar to that for mainshocks only (independent seismicity), except for higher magnitude earthquakes due to the limited number of data available. The expected PGA values are examined further by comparing the values with the actual PGA from earthquakes in the Sausu Fault region, including the damaging 29 May 2019 earthquake. Depending on the earthquake magnitude, the GMPEs may overestimate or underestimate the PGA values. In addition, the residual analyses are conducted to examine trends of the expected PGA values. [ABSTRACT FROM AUTHOR]

In the subduction zone off the west coast of central Sumatra, two great earthquakes, the 2007 great Bengkulu earthquake (Mw 8.4) and the 2010 Mentawai tsunami earthquake (Mw 7.8), occurred along the plate interface. Although the moment magnitude of the 2010 earthquake was much smaller than that of the 2007 earthquake, the tsunami heights resulting from the former 2010 earthquake were higher than those resulting from the latter 2007 earthquake, indicating that tsunami heights are difficult to forecast. An advanced method for determining appropriate source models that can explain the tsunami heights along coastal areas is needed for tsunami warning purposes. In this study, fault parameters were estimated from the W-phase inversion, and fault length and width were calculated from suitable scaling relations between those and the magnitude for the 2007 and 2010 earthquakes. Tsunami numerical simulations were conducted using various slip amounts or corresponding rigidities. The best slip amount or corresponding rigidity was selected by comparing the measured and computed tsunami heights. For the 2007 Bengkulu earthquake, the measured tsunami heights are well explained using a rigidity of 3.0 × 1010 Nm−2 (7.59-m slip amount). For the 2010 Mentawai tsunami earthquake, the measured tsunami heights are well explained using a rigidity of 1.5 × 1010 Nm−2 (8.17-m slip amount). From those results, we determined the depth-dependent rigidity relation for Central Sumatra to estimate appropriate source models in our tsunami height forecasting method. [ABSTRACT FROM AUTHOR]

Recent earthquake activity has brought about extensive structural damage and loss of life. The adverse effects of earthquakes on the economic sector can be seen all over the world, particularly in developing countries. This calls for those developing countries to adhere to various methods to combat these effects. Buildings serving the educational needs of the people can also contribute by accommodating people in case of emergencies and disaster. Therefore, these buildings must be evaluated in terms of their capacity and strength in the face of earthquakes. This study will employ the Rapid Visual Screening (RVS) technique to evaluate the seismic vulnerability condition of nine reinforced concrete educational buildings at Jenderal Soedirman University, Indonesia, five located in Purbalingga, and four in Purwokerto. The results of the study allow the authorities concerned to devise a prioritization plan regarding the structural safety of all of the educational buildings at Jenderal Soedirman University, Indonesia. [ABSTRACT FROM AUTHOR]

High magnitude flash flood has occurred several times in some areas in Central Sulawesi Province after the 2018 Palu Earthquake, one of them is in the Bangga River, Sigi Regency, Indonesia. It has caused massive impacts such as damaging agricultural and plantation areas and submerging public facilities and infrastructure and even causing fatalities. The flood carries a variety of materials, especially high concentration sediments which are thought to originate from eroded soils due to landslides induced by a 7.5 magnitude earthquake. These materials are eroded and transported by the flow at the upstream watershed due to heavy rainfall. This study intends to investigate the potential of landslides, factors that trigger floods and increased flooding after the earthquake. This research was conducted by investigating the landslides potency based on field surveys and interpretation of the latest satellite imagery, analyzing the characteristics of rainfall as a trigger for flooding, and predicting the flood potency as the primary impact of these two factors. Rainfall-flood transformation was simulated with the HEC-HMS Model, one of the freeware semi-distributed models commonly used in hydrological analysis. The model input is the configuration of river networks generated from the National DEM (DEMNAS), hourly rainfall during floods and other watershed parameters such as land cover, soil types and river slope. The similar simulation was also carried out on the condition of the watershed before the earthquake. Based on the results of the analysis, It can be inferred that flash floods in the Bangga River are mainly caused by heavy rainfall with long duration and landslide areas in the upper watershed triggered by the 2018 Palu Earthquake with an area of approximately 10.8 km2. The greatest depth of rainfall as a trigger for flooding is 30.4 mm with a duration of 8 hours. The results of the study also showed that landslides in the upper watershed could increase the peak flood by 33.33% from 118.56 m3/s to 158.08 m3/s for conditions before and after the earthquake. [ABSTRACT FROM AUTHOR]

On September 28, 2018, the Mw 7.5 earthquake occurred in Palu, Central Sulawesi, Indonesia. This earthquake produced strong tremors, landslides, liquefaction and a tsunami and caused thousands of fatalities and damaged houses and infrastructure. We have relocated 386 of the 554 Palu aftershocks by using the double-difference relocation method (hypoDD) from September 28 to November 22, 2018. The aftershock pattern is consistent with the crustal deformation in the area and generally shows that the events have a NW–SE trending of ~ 200 km in length and ~ 50 km in width. Most of the aftershocks are located to the east of the Palu-Koro Fault Line. Since November 2, 2018, there have been hundreds of swarm earthquakes in the area of Mamasa, West Sulawesi, which is about 230 km south of the city of Palu. Some of these earthquakes were felt, and houses were even damaged. We have relocated 535 of the 556 swarm earthquakes having a magnitude of M 2 to M 5.4. Our results show that the seismicity pattern has a dip that becomes shallower to the west (dipping at a ~ 45° angle) and extends from north to south for a length of ~ 50 km. We also conducted a focal mechanism analysis to estimate the type of fault slip for selected events of an M > 4.5 magnitude. Most of the solutions of the focal mechanism analysis show a normal fault type. This swarm earthquake probably corresponds to the activity of the fault in the local area. [ABSTRACT FROM AUTHOR]

An earthquake with a magnitude of Mw=7.5 that occurred in Sulawesi, Indonesia, on 28 September 2018 triggered liquefaction and tsunamis that caused severe damage and many casualties. This paper reports the results of a post-tsunami field survey conducted by a team with members from Indonesia and Taiwan that began 13 d after the earthquake. The main purpose of this survey was to measure the run-up of tsunami waves and inundation and observe the damage caused by the tsunami. Measurements were made in 18 selected sites, most in Palu Bay. The survey results show that the run-up height and inundation distance reached 10.7 m in Tondo and 488 m in Layana. Inundation depths of 2 to 4 m were common at most sites and the highest was 8.4 m in Taipa. The arrival times of the tsunami waves were quite short and different for each site, typically about 3–8 min from the time of the main earthquake event. This study also describes the damage to buildings and infrastructure and coastal landslides. [ABSTRACT FROM AUTHOR]

Tasikmalaya is one of the earthquake-prone cities in Indonesia as a result of collision of the Indo-Australian and the Eurasian plate. Earthquake mitigation efforts are needed to reduce the impact of future earthquakes. One of the mitigation efforts that can be proposed is a re-evaluation of the seismic hazard of the city. The main objective of this study was to re-evaluate seismic hazard expressed in Peak Ground Acceleration (PGA) and spectral acceleration at bedrock level based on a probabilistic approach, particularly in Tasikmalaya City. We first processed the earthquake data then adopted the new 22 seismogenic structures as the earthquake sources. Furthermore, we determined the characterization of each earthquake sources, selected, and adjusted the ground motion attenuation, and logic tree processed to manage the uncertainty of earthquake recurrence, magnitude distribution, and ground motion attenuation. Using Probabilistic Seismic Hazard Analysis (PSHA), PGA and spectral acceleration at bedrock level corresponding to 2% exceedance of 50 years' probability were calculated. The seismic hazards were quantified in terms of PGA and spectral acceleration at two fundamental periods of 0.2 and 1.0 s. The results showed that the subduction interface zones in southern Java and background seismicity significantly contributed to the seismic hazard in Tasikmalaya City. If compared with the 2010 Indonesian earthquake hazard maps, the results have relatively higher values in the three hazard maps which might due to the different characterization of earthquake sources, earthquake catalogs, and the GMPE to be used. [ABSTRACT FROM AUTHOR]

On 28th September 2018, a magnitude 7.5 earthquake occurred on the Palu-Koro strike slip fault near Palu, Indonesia. Shortly after, large tsunami waves generated by the earthquake and the submarine landslides it triggered, washed into Palu Bay. Here, we describe sediment characteristics of the tsunami deposits and present wave height models to provide a modern analogue for tsunamis occurring on strike slip faults. We analyzed 51 sediment samples from 21 sampling points on two transects at Palu City and one transect at Pantaloan. At Palu City, the tsunami inundated between 250 and 270 m inland. Sediments were massive, with landward fining from coarse sands (φ 0) to fine sands (φ 3.7) and weak upward fining sequences (by up to 1 φ). At Pantaloan the tsunami inundated up to 275 m inland. Sediments were massive, with landward fining from a few grains of gravel (φ −2) and coarse sands (φ 0.5) to fine sands (φ 2.5) and weak upward fining sequences (by up to 1 φ). Based on the sediment data the TSUFLIND model predicted: at Palu city flow depths of 1 to 8 m, and flow velocities up to 3.9 m/s; and at Pantoloan flow depths of 2 to 8 m, and flow velocities up 3.8 m/s. The boulder transport model was applied to data from heavy concrete blocks (0.8 to 4.9 tons) deposited by the tsunami between 46 and 125 m inland, and predicted flow depths of 0.8 to 4.3 m and flow velocities up to 5.6 m/s. The rapid attenuation inland of the tsunami flow depth is consistent with the event being partially generated by landslides caused by the Palu-Donggala earthquake. A study of Dutch colonial archives and historical data reveals at least six tsunami events have occurred in or near Palu Bay since 1920, suggesting a very short return period for such events, and a significant tsunami hazard to the area. • Palu-Donggala tsunami reached flow depths of up to 8 m. • Palu-Donggala tsunami reached flow velocity of up to 5.6 m/s. • Palu-Donggala tsunami was destructive within the initial 100 m but rapidly diminished in intensity beyond. • Six tsunamis occurred in or near Palu Bay since 1920, suggesting a significant tsunami hazard to the area. [ABSTRACT FROM AUTHOR]

On September 28,2018, a 7.5 magnitude earthquake struck the island of Sulawesi, Indonesia. The epicentre was the provincial capital of Palu, located on a bay on the island’s northwest coast. The quake triggered a tsunami that swept 10-meter tall waves of seawater and swamped the city. The combination of the earthquake, tsunami, soil liquefaction and landslides claimed well over 2000 lives, destroyed homes, buildings, infrastructures and farmland in several districts. Recognizing the need to relocate settlements from the liquefaction-prone areas, the Indonesian government developed the Master Plan for Recovery and Reconstruction for Central Sulawesi through the EARR and SWIP projects. Indra and Planetek Italia contributed to the implementation of this plan with a batch of EO-based services. The main information provided was related to terrain deformation mapping (before the earthquake)followed by the update of terrain information mapping (in the months immediately after the earthquake)and reconstruction monitoring with Very High Resolution images. The collaboration went on with a capacity-building workshop and aknowledge transfer activity held in Jakarta in June 2019 regarding the technical aspects of the delivered products and training sessions for local users to teach them to use the Geohazards Exploitation Platform (GEP) of ESA. [ABSTRACT FROM AUTHOR]

Large subduction earthquakes have repeatedly occurred along the Sumatra subduction zone, where the Australian oceanic plate is subducting beneath the Sunda continental plate. We have analyzed two years (2009 to 2011) earthquake data from a regional seismic network along the Sumatra region that provided by the Badan Meteorologi, Klimatologi, dan Geofisika (BMKG) of Indonesia. Based on those data, a regional one-dimensional velocity model was refined first. Then, all events have been relocated based on the hypocenter double difference technique. Based on the relocated earthquake catalogue, three large earthquake sequences with magnitude greater than Mw 7.5 were well identified with one of them induced significant tsunami, thus, the 30 September 2009 Mw 7.6 Padang earthquake, the 7 April 2010 Mw 7.8 Banyak Islands earthquake, and the 25 October 2010 Mw 7.8 Mentawai tsunami earthquake. The characteristics of these earthquake sequences were analyzed and its possible implications were discussed in this study. A statistical analysis of polynomial linear fitting has been proposed to identify lineation of earthquake pattern in this study. Results indicated that a northwest-southeast dipping of earthquake lineation was identified within the Banyak Islands earthquake sequence and considered as the activity of the upper splay fault. Limited earthquake activity was identified at the Mentawai gap region and considered as a locked asperity. Those faults could be as a major threat of a great source of tsunamigenic fault. This region is considered as a high potential candidate to generate destructive earthquake and tsunami on the Sumatra subduction zone in future. [ABSTRACT FROM AUTHOR]

In this paper we investigated the phenomenon of extreme run-up at Babi Island in Indonesia caused by the 1992 Flores earthquake (Mw = 7.8) using a series of three-dimensional numerical modeling experiments. Simulations were carried out to investigate how much the presence/absence of the coast of Flores affects the generation of the extreme inundation at Babi Island through the reflection process of tsunami waves. [ABSTRACT FROM AUTHOR]