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We present analysis of the December 2018 Anak Krakatau tsunami in Sunda Strait, Indonesia, from a combination of post-tsunami field surveys, bathymetric changes and spectral analysis of the tsunami tide gauge records. Post-tsunami surveys revealed moderate tsunami height along the coast of Sumatra and Java with maximum surveyed runup of 13.5 m and maximum inundation distance of 330 m. At small islands located close to the volcano, extreme tsunami impacts were observed indicating not only a huge tsunami was generated by large amounts of collapse material which caused notable changes of seafloor bathymetry, but also indicates the role of those small islands in reducing tsunami height that propagated to the mainland of Indonesia. Our spectral analysis of tide gauge records showed that the tsunami's dominant period was 6.6–7.4 min, indicating the short-period nature of the 2018 Sunda Strait tsunami. [ABSTRACT FROM AUTHOR]

The strike-slip earthquake on 28 September 2018 (Mw 7.5) along the Palu-Koro fault on Sulawesi Island has raised concerns about the potential impact of tsunamis generated by submarine landslides in Palu Bay, Indonesia. The horizontal displacement of the Palu-Koro fault generated landslide tsunamis that covered Palu Bay, creating wave-related hazards along the coastal area. Based on the unusual amount of information on this tsunami, this study investigated possible sources using the available preliminary data. The generation of comparatively small tsunamis by coseismic seafloor deformation is omitted, and only tsunamis generated by submarine/subaerial landslides are analyzed in this study. Two-layer modeling (soil and water) based on the shallow-water equation was used to simulate the tsunami propagation in the bay with severe, moderate, and minor impacts. The accuracy of the model was validated based on the waveform at the Pantoloan tidal gauge and trace data. The tsunami heights from a combination of small to large submarine landslides could reach up to 3.0–7.0 m along the Palu shores. This model focused on studying the effects of the tidal level on coastal inundation in Palu Bay, using the 2018 Palu tsunami event as a benchmark scenario, to demonstrate the capabilities of the model. One result shows that, regardless of the tidal level, the 2018 Palu tsunami, which occurred during high tide, will always result in flooding, with a maximum tsunami height of up to 7.0 m above mean sea level. The main results suggest two causes for this tsunami event: the tsunami source and the topography. First, the model requires one large source at the bay entrance to reproduce the arrival time (approximately 5 min) and the large wave observed at the Pantoloan gauge. To reproduce the later waves, small sources in the bay (S1–S6) and minor large sources (L2 and L3) are needed. Second, the datum correction for the terrain is changed to improve the accuracy of the water level. Additionally, the removal of buildings from the topography is important to achieve highly accurate flow depths and to obtain an inundation area close to the real situation. The impacts along the coastline of Palu Bay from peak waves can be used to identify tsunami hazards in the area in the future. [ABSTRACT FROM AUTHOR]

Regional disaster data are important for understanding the characteristics of disasters and for identifying potential mitigation measures. However, many countries have no official disaster database that includes information such as numbers of deaths or damaged buildings for each disaster event. The Global Centre for Disaster Statistics (GCDS) was established to assist countries and organizations in the collection of disaster data. At present, a significant amount of tsunami disaster data are available from Indonesia, which will be used to demonstrate its application for analyzing vulnerability characteristics of historical tsunamis. There are 53 data points covering 13 tsunami events between the year 1861 and 2014. Based on data availability, five tsunami events, namely the 1977 Sumba, the 2004 Indian Ocean, the 2006 Java, the 2010 Mentawai, and the 2011 Great East Japan, were selected. Numbers of deaths and damaged buildings were used in combination with hazard data to estimate vulnerability, defined as the ratio between maximum flow depth against death and building damage ratios. Numbers of evacuees were initially used to estimate actual numbers of exposed population but it was later discovered that this parameter overestimated the exposed population in certain cases. As a result, this study presents the vulnerability characteristics of people and buildings in Indonesia, exposed to unusual or extreme tsunamis, mostly in a condition without or with limited access to official warnings. In brief, a maximum flow depth of 5 m caused an approximate 100% death ratio in the majority of Indonesian tsunamis in this study. On the other hand, death ratio in the 2011 Japan tsunami was limited to 10% because of the early warning and high disaster awareness. Effective disaster risk reduction activities such as official warnings, evacuations, and tsunami education were observed for certain locations. Lastly, adding hazard and population data at the village level is recommended for improving the collection of future tsunami disaster data for the GCDS database. [ABSTRACT FROM AUTHOR]

The height of the tsunami caused by the Sulawesi earthquake in 2018 was higher than that estimated from the magnitude of the earthquake, and its cause is not well understood. Although it is conceivable that tsunamis originated from landslides in several cases, it is not known whether landslides were occurring in the coastal area at the time. This report describes the results of a field survey conducted to investigate the traces of subsidence and the characteristics of the tsunami incidents in the bay far fromthe epicenter. Subsidence was observed at a minimum of seven points along the coast; in accord with the reports of eyewitnesses, this suggests that subsidence might have generated tsunamis. [ABSTRACT FROM AUTHOR]

On September 28, 2018, following a magnitude 7.5 strike-slip fault earthquake, an unexpected tsunami inundated the coast of Palu bay, Sulawesi, Indonesia, causing many casualties and extensive property damage. However, the earthquake's mechanism rarely generates a destructive tsunami. The tidal record at Pantoloan, located along the coast of Palu bay, indicates that the tsunami arrived 6 min after the earthquake and generated 2 m of receding water. It had a maximum wave height of 2 m and arrived approximately 2 min later. The tsunami had a relatively short period and caused devastation as far inland as 300 m. Additionally, 8 m high watermarks were observed near the coast; the flow depth decreased to 3.5 m inland (Fig. 1). Amateur videos and eyewitness accounts indicate that the tsunami did not enter the bay through its mouth but obliquely from an area inside the bay. Our hypothesis, therefore, is that the killer tsunami was most likely generated by an underwater landslide occurring inside Palu bay. While detailed bathymetric data are still needed to confirm this hypothesis, in this article we provide a preliminary analysis of the available data, supported by the results of a field survey, to strengthen this hypothesis and provide direction for further post-tsunami surveys and analysis. [ABSTRACT FROM AUTHOR]

This paper describes the examination of three practical tsunami run-up models that can be used to assess the tsunami impact on human beings in densely populated areas. The first of the examined models applies a uniform bottom roughness coefficient throughout the study area. The second uses a very detailed topographic data set that includes the building height information integrated on a Digital Elevation Model (DEM); and the third model utilizes different bottom roughness coefficients, depending on the type of land use and on the percentage of building occupancy on each grid cell. These models were compared with each other by taking the one with the most detailed topographic data (which is the second) as reference. The analysis was performed with the aim of identifying how specific features of high resolution topographic data can influence the tsunami run-up characteristics. Further, we promote a method to be used when very detailed topographic data is unavailable and discuss the related limitations. To this purpose we demonstrate that the effect of buildings on the tsunami flow can be well modeled by using an equivalent roughness coefficient if the topographic data has no information of building height. The results from the models have been utilized to quantify the tsunami impact by using the tsunami casualty algorithm. The models have been applied in Padang city, Indonesia, which is one of the areas with the highest potential of tsunami risk in the world. [ABSTRACT FROM AUTHOR]

Taxonomic status and type specimens of Platycephalus bataviensis Bleeker , described based on two syntypes (110 and 140 mm TL) from Batavia (= Jakarta), are discussed. Four platycephalid specimens have been recognized as possible syntype(s) of P. bataviensis. Of them, a specimen of 140.5 mm TL deposited at Muséum National d'Histoire Naturelle, Paris, identified as Inegocia japonica, is regarded to be the larger syntype and is designated as the lectotype of P. bataviensis in this study, while the paralectotype of the species is not identified. As a result, P. bataviensis becomes a junior synonym of I. japonica. [ABSTRACT FROM AUTHOR]

Fragility functions, as new measures for estimating structural damage and casualties due to tsunami attack, are developed by an integrated approach using numerical modeling of tsunami inundation and GIS analysis of post-tsunami survey data of the 2004 Sumatra–Andaman earthquake tsunami disaster, obtained from Banda Aceh, Indonesia. The fragility functions are expressed as the damage probabilities of structures or death ratio with regard to the hydrodynamic features of tsunami inundation flow, such as inundation depth, current velocity and hydrodynamic force. They lead to the new understandings of the relationship between local vulnerability and tsunami hazard in a quantitative manner. [ABSTRACT FROM AUTHOR]

Discusses the sedimentation process which is caused by modern tsunami in relation to geologic and numerical investigations in Indonesia. Deposition of marine sand on the shore lines; Destructiveness of the waves; Explanation for destructiveness; Results of test; Reference material available.

Following the eruption of Mount Anak Krakatau, a considerable landslide occurred on the southwestern part of the volcano and, upon entering the sea, generated a large tsunami within the Sunda Strait, Indonesia, on December 22, 2018. This tsunami traveled ~ 5 km across the strait basin and inundated the shorelines of Sumatra and Java with a vertical runup reaching 13 m. Following the event, observed field data, GPS measurements of the inundation, and multibeam echo soundings of the bathymetry within the strait were collected and publicly provided. Using this dataset, numerical modeling of the tsunami was conducted using the two-layer (soil and water) TUNAMI-N2 model based on a combination of landslide sources and bathymetry data. The two-layer model was implemented to nest the grid system using the finest grid size of 20 m. To constrain the unknown landslide parameters, the differential evolution (DE) global optimization algorithm was applied, which resulted in a parameter set that minimized the deviation from the measured bathymetry after the event. The DE global optimization procedure was effective at determining the landslide parameters for the model with the minimum deviation from the measured seafloor. The lowest deviation from the measured bathymetry was obtained for the best-fitting parameters: a maximum landslide thickness of 301.2 m and a landslide time of 10.8 min. The landslide volume of 0.182 km3 estimated by the best-fitting parameters shows that the tsunami flow depth could have reached 3–10 m along the shore with a K value of 0.89, although the simulated flow depths were underestimated in comparison with the observation data. According to the waveforms, the general wave pattern was well reproduced at tide gauges during the event. A large number of objective function evaluations were necessary to locate the minimum with the DE procedure to fix the grid cell size to 20 m; this limited the accuracy of the obtained parameter values for the two-layer model. Moreover, considering the generalizations in the modeling of landslide movements, the impact landslide time and thickness must be carefully calculated to obtain a suitable accuracy. [ABSTRACT FROM AUTHOR]

We report herein on a 20-year-old Japanese man who was referred to our hospital for fever and diarrhea after returning from Indonesia. On admission, his blood test was essentially normal, besides a slight elevation in inflammatory markers. After excluding malaria and dengue fever, empiric use of ceftriaxone was initiated for suspected enteric fever, which was unsuccessful. However, drastic clinical improvement was observed after initiation of minocycline. The polymerase chain reaction test for Rickettsia typhi was positive from serum samples on admission, confirming the diagnosis of murine typhus. Although rarely seen in Japan, clinicians should be aware of this disease when examining patients with fever coming back from murine typhus endemic areas.