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Distribution of the measured tsunami flow depth (blue) and runup (red) in Sumatra and Java coasts due to the December 2018 Anak Krakatau tsunami in Sunda Strait, Indonesia
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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...
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Context 1
... Lampung Province, tsunami traces were measured at 15 points where flow depth reached 2.9 m and maximum tsunami inundation distance was up to 150 m at Kunjir Village, Rajabasa Subdistrict (Fig. 2). Measurements in Lampung were mostly made in Rajabasa Subdistrict since tsunami traces were less visible in other places. In this region, the average tsunami flow depth was 1.5 m and it inundated coastal areas as far as 50 m from the coast, on the average (Tables 1, ...
Context 2
... the south at a narrow bay named Lada Bay located at 6.4°S-6.53°S and 105.68°E-105.82°E (see location in Fig. 2), almost no tsunami trace was observed, although such a narrow bay has the potential to amplify tsunami heights. One reason that the area inside the bay was less affected by the tsunami is the fact that the bay is relatively sheltered by Tanjung Lesung peninsula, a most attractive tourism destination in the region, which was itself ...
Context 3
... order to reveal the notable bathymetric changes through making cross-sections of the bathymetric data, we extracted the bathymetric data of the 2016 and 2018 surveys along the cross-section line a'-b' in Fig. 7 (see the 2016 and 2018 survey traces in Figs. S2-S4). This cross-section line has water depths of 150 m in the north and 255 m in the south based on the 2016 bathymetric data. By analyzing the posteruption bathymetry data, we observed an increase in the seafloor elevation towards south, indicating that the collapse material spread out not only to the west (as indicated by the visible ...
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On 22 December 2018, volcanic activity of Anak Krakatau, Indonesia, triggered a tsunami that caused more than 437 casualties on surrounding coastlines. Soon after the event, before the physical evidence of the tsunami disappeared, a postevent field survey was carried out. Measurements of tsunami inundation and impact are important to better model a...
Citations
... In coastal environments, eruptions can be associated with volcano-induced tsunamis. These tsunamis can be produced by a broad range of sources (volcano-related earthquakes, partial sector collapses, pyroclastic flows, underwater explosions, caldera-forming eruptions, Paris (2015) with serious consequences, as shown by recent events in 2019 at Krakatoa (Muhari et al. 2019) and 2022 at Hunga Tonga Hunga Ha'apai (Terry et al. 2022). In the case of future phonolitic eruptions on Petite-Terre, explosive activity could trigger volcanogenic tsunamis during the initial stage of the eruption or even at a later stage if a rapidly rising cone were to become destabilized. ...
We studied four Quaternary volcanic phonolitic explosive edifices on Petite-Terre Island (Mayotte, Comoros Archipelago, Western Indian Ocean) to quantify magma fragmentation processes and eruptive dynamics. Petite-Terre explosive volcanism is the westernmost subaerial expression of a 60-km-long volcanic chain, whose eastern tip was the site of the 2018–2020 submarine eruption of the new Fani Maoré volcano. The persistence of deep seismic activity and magmatic degassing along the volcanic chain poses the question of a possible reactivation on land. Through geomorphology, stratigraphy, grain size, and componentry data, we show that Petite-Terre “maars” are actually tuff rings and tuff cones likely formed by several closely spaced eruptions. The eruptive sequences of each edifice are composed of thin (cm–dm), coarse, lithic-poor pumice fallout layers containing abundant ballistic clasts, and fine ash-rich deposits mostly emplaced by dilute pyroclastic density currents (PDCs). Deposits are composed of vesiculated, juvenile fragments (pumice clasts, dense clasts, and obsidian), and non-juvenile clasts (from older mafic scoria cones, coral reef, the volcanic shield of Mayotte, as well as occasional mantle xenoliths). We conclude that phonolitic magma ascended directly and rapidly from depth (around 17 km) and experienced a first, purely magmatic fragmentation, at depth (≈ 1 km in depth). The fragmented pyroclasts then underwent a second shallower hydromagmatic fragmentation when they interacted with water, producing fine ash and building the tuff rings and tuff cones.
... Submarine volcanoes have the potential to bring severe damage to local and even global societies with volcanic tsunamis, as highlighted by recent tsunami events related to the 15 January 2022 eruption of Hunga Tonga-Hunga Ha'apai, Tonga (e.g., Borrero et al., 2023;Kubo et al., 2022;Kubota et al., 2022;Lynett et al., 2022;Purkis et al., 2023), or the 22 December 2018 eruption of Anak Krakatau, Indonesia (e.g., Grilli et al., 2019;Heidarzadeh, Ishibe, et al., 2020;Heidarzadeh, Putra, et al., 2020;Muhari et al., 2019;Mulia et al., 2020;Ye et al., 2020), and by historical events listed in Day (2015) and Paris et al. (2014), some of which caused over hundreds to thousands of fatalities. Yet, it is often challenging to investigate submarine volcanoes due to the lack of on-site monitoring systems. ...
Submarine volcano monitoring is vital for assessing volcanic hazards but challenging in remote and inaccessible environments. In the vicinity of Kita‐Ioto Island, south of Japan, unusual M ∼ 5 non‐double‐couple volcanic earthquakes exhibited quasi‐regular recurrence near a submarine caldera. Following the earthquakes in 2008 and 2015, a distant ocean bottom pressure sensor recorded distinct tsunami signals. In this study, we aim to find a source model of the tsunami‐generating earthquake and quantify the pre‐seismic magma overpressure within the caldera's magma reservoir. Based on the earthquake's characteristic focal mechanism and efficient tsunami generation, we hypothesize that submarine trapdoor faulting occurred due to highly pressurized magma. To investigate this hypothesis, we establish mechanical earthquake models that link pre‐seismic magma overpressure to the size of the resulting trapdoor faulting, by considering stress interaction between a ring‐fault system and a reservoir of the caldera. The trapdoor faulting with large fault slip due to magma‐induced shear stress in the submarine caldera reproduces well the observed tsunami waveform. Due to limited data, uncertainties in the fault geometry persist, leading to variations of magma overpressure estimation: the pre‐seismic magma overpressure ranging approximately from 5 to 20 MPa, and the co‐seismic pressure drop ratio from 10% to 40%. Although better constraints on the fault geometry are required for robust magma pressure quantification, this study shows that magmatic systems beneath calderas are influenced significantly by intra‐caldera fault systems and that tsunamigenic trapdoor faulting provides rare opportunities to obtain quantitative insights into remote submarine volcanism hidden under the ocean.
... Thus, the Indonesian highly complex, volcano-tectonic setting comprises convergent plate boundaries, extending from off the west coasts of the north Sumatera to the Banda Arc in the eastern provinces, making both ground-based and coastal regions in Indonesia vulnerable to geological disasters that include tectonic earthquakes, tsunamis and volcanic eruptions. While the primary cause for tsunami generation and its corresponding propagation is attributable to earthquake of tectonic origin for global observations [5], in the Indonesian context, however, previous studies on possible tsunami sources also pointed out volcanic processes [6,7] and landslides [8][9][10] as potential sources of such a disaster, in addition to seismic sources [11,12]. As the potency for geological hazards in Indonesia is large enough and in the light of increasingly widespread dense population in domestic regions [13] prone to these hazards, research focusing on this subject is of significance. ...
Earth Physics Research Group (EPRG) is one of three groups of research running at Physics Study Program, the State University of Surabaya, Indonesia, where a number of research projects with corresponding topics have been conducted (and some are in progress) by the group members and associated students having final projects in the field of earth physics since 2018. Whereas the research roadmap of the group has been presented in association with definitive research projects for 25 years long starting from 2011, the specific goal of this paper is to shortly summarise all academic achievement in terms of research performance made by the group members during the last five years. The majority of the recent works was mainly based on computational work, where some were completed in collaboration with researchers from other universities and a national agency and others were performed by the group members and selected students. The topics were spread across disciplines in earth physics that included tectonic earthquakes, tsunami generation and propagation of seismic and non-seismic origin, volcanic eruptions and an integrated disaster mitigation study. A small portion of the projects were performed using a chosen method of applied geophysics. These studies have ended up with publications in recent years, where the saline points of the key findings are here presented. Future studies focusing on vulnerability to earthquake hazards in the northern areas of Java and on volcanic and meteo-tsunamis are also discussed in the context of possible tsunamis induced by seismic sources or volcanic processes.
... The 2018 tsunami events in Palu and Sunda Strait highlighted the limitations and vulnerabilities of the existing InaTEWS, particularly in addressing non-tectonic tsunamigenic events like mid-sea volcanic eruptions and underwater landslides. Moreover, the initiatives taken by the Indonesian government after 2018, such as the installation of additional equipment around Anak Krakatau, making it the most equipped tsunami warning system in Indonesia (Husrin et al., 2021;Muhari et al., 2019), were commendable. ...
To help optimize tsunami warning system in Indonesia, particularly concerning non-seismically inducted tsunamis and at the subnational level, this study employs a qualitative methodology to draw lessons from the Anak Krakatau-induced tsunami on December 22, 2018. A total of 37 community members and 35 government officials in Pandeglang Regency and at the national level participated in in-depth interviews and focus groups discussions. Participants emphasized bureaucratic mismatches and delays, underlining the urgent need for clearer national-subnational communication. The study presents concrete and actionable recommendations for refining warning reception, decision-making, legitimization processes and warning dissemination. Proposed changes such as diversifying information sources and localizing tsunami siren control aim to empower local entities and expedite responses, overall increasing community preparedness for future tsunami threats. By contrasting the experiences and recommendations of affected communities, local government and national-level actors, the study makes a case for improving warning systems based on the past experience and recommendations of the first concerned and first impacted.
... Most of the Anak Krakatau eruptive products are basaltic to andesitic lava flows and volcanic bombs (Westerveld, 1952;Camus et al., 1987;Dahren et al., 2012). The most significant activity during the past few years was the 2018 eruption that generated landslides due to volcanic flank failure and caused tsunamis that hit the southeast coast of Sumatra and west of Java killing more than 400 people (Muhari et al., 2019;Walter et al., 2019;Novellino et al., 2020;Ye et al., 2020;Grilli et al., 2021;Hunt et al., 2021;Cutler et al., 2022). However, Anak Krakatau continues to grow, and its recent eruptions mostly produce lava flows and volcanic ash . ...
Understanding the evolution of magma storage conditions on volcanoes which have had more than one caldera-forming eruption (CFE) is important to know about past and present conditions, as a key to forecast future potential hazards. Krakatau volcano is characterized by cyclic phases of growth and destruction of the edifice. A volcanostratigraphic study identified three eruptive periods: Old Krakatau, Young Krakatau, and Anak Krakatau. The Old and Young Krakatau periods ended with the first and second CFE respectively. Due to its permanent activity and edifice evolution, Krakatau poses a high risk on the surrounding inhabited islands. In this study, we combined geochemistry, rock magnetic, and petrology to infer the evolution of magma storage conditions from Old to Anak Krakatau periods. This study is the first to report on the chemical and rock magnetic characteristics, as well as storage system conditions of Old Krakatau and its relation to the ongoing evolution of Krakatau. Our data show that: 1) Old and Young Krakatau magma storage regions are shallow (within the upper 3 km), contain more differentiated magmas, from which the Old Krakatau magmas may be less oxidized and had lower temperatures than Young Krakatau; 2) Anak Krakatau magma storage is deeper (up to 26 km), less differentiated, and erupted hotter but more reduced compared to Old and Young Krakatau. The Old and Young Krakatau lavas were the products of pre-CFE and their chemical characteristics are included at maturation phase, whereas the Young Krakatau pumice samples were the product of the second CFE. Lastly, the post-second CFE activity of AK is currently in an incubation phase and represented by mafic products of frequent and small eruptions. Knowing that the volcano has experienced maturation and CFE phases in the past, the current AK may evolve to those phases in the future.
... The 2018 tsunami case was generated as a result of a large volume of volcanic material from Anak Krakatau volcano ( Figure 1) that collapsed into the sea (Grilli et al., 2019;Heidarzadeh et al., 2020a). This tsunami event significantly affected the vicinity across Sunda Strait with recorded maximum tsunami runup height and inundation distance of 13.5 m and 330 m, respectively, along the coasts of Java and Sumatra (Muhari et al., 2019). The Sunda Strait has been identified as an area prone to volcanic tsunamis due to the intense volcanic activity of Anak Krakatau volcano. ...
... The initiation volume of the sector collapses is also complex by broad variety of generation mechanisms, from small slides to large avalanches. Uncertainties in the exact source mechanism of the volcanic sector collapse leave major challenges to construct a real-time tsunami forecasting (Grilli et al., 2019;Muhari et al., 2019). ...
Present tsunami warning systems have been specialized for earthquake-generated tsunamis, but rapidly evaluating the tsunamis caused by volcanic eruptions and/or volcanic sector collapses remains a challenge. In this study, we applied a numerical model to the 2018 Anak Krakatau tsunami event, which was generated by the sector collapse, investigated a tsunami prediction skill by the model, and developed a real-time forecasting method based on a pre-computed database for future tsunamis accompanied by such eruption of Anak Krakatau. The database stores spatiotemporal changes in water surface level and flux, which are simulated under various collapse scenarios, for confined areas in the vicinity of potential source. The areas also cover the locations of observation stations that are virtually placed on uninhabited island surrounding the source area. During an actual volcanic tsunami event, a tsunami is expected to be observed at the observation stations. For real-time tsunami forecasting, the most suitable scenarios to reproduce the observed waveforms are searched quickly in the database. The precomputed results under the identified scenarios are further provided as input for rapid tsunami propagation simulation. Therefore, an effective real-time forecasting can be conducted to densely populated coastal areas located at a considerable distance from the source, such as the coasts of Java and Sumatra. The forecasting performance was examined by applying the method for three hypothetical collapse scenarios assuming different sliding directions. We demonstrated that the tsunamis along the coasts were successfully forecasted. Moreover, we showed that the combination of a pre-computed database and the existence of observation stations near the source area was able to produce appropriate tsunami forecasting for the coastal area even in a volcanic event.
... One is the volcanic tsunami threat in the Sunda Strait. On 22 December 2018, a giant tsunami occurred, affected by a lateral collapse on the southwest flank of Anak Krakatau (AK) (Grilli et al., 2019;Muhari et al., 2019). According to BNPB (National Disaster Management Authority) in 2019, casualties resulted from that event 437 people were killed, more than 7200 injured, should be investigated. ...
This study examines the agent behavior during a complex tsunami process to reach designated shelters based on the agent-based modeling approach. A GIS-based tsunami inundation modeling is employed considering the land slope and surface roughness coefficient to estimate the tsunami height loss. This model becomes the basis for determining the service area within the study site. Five shelter candidates are assessed using agent-based modeling simulated in the NetLogo, implementing the 50 minutes ETA and 9 meters tsunami run-up propagation for four population age classifications. Overall, the Panimbang coastal area is categorized as a high vulnerability to tsunamis (14.68% of the total area), where the run-up propagation is extended due to the tsunami invading rivers, thereby increasing the risk toward local society. Of particular concern, two proposed shelters (SA1 and SA5) exceed the capacity by 12.43% and 59.44% of their maximum capacity, respectively. Of 9,640 agents (people) simulated, 77.7% are evacuated, and 22.3% fail to reach the shelters, with a majority of the adult category. A sufficiently high casualty number is due to a "bottleneck" in the overlapping service areas. However, reconsidering the overcapacity TES with some additional shelters in the surrounding area is recommended.
... In coastal environments, eruptions can be associated with volcanic-induced tsunamis. These tsunamis can be produced by a broad range of sources (volcanic earthquakes, partial sector collapses, pyroclastic ows, underwater explosions, caldera-forming eruption, Paris, 2015a) with serious consequences as shown by recent events in 2019 at Krakatoa (Muhari et al., 2019) and 2022 at Hunga Tonga Hunga Ha'apai (Terry et al., 2022). In the case of future phonolitic eruptions on Petite-Terre, explosive activity could trigger volcanogenic tsunamis during the initial stage of the eruption or even at later stages when the rapidly rising cones are destabilized even though no evidence was found on the eld. ...
We describe four Quaternary volcanic phonolitic explosive edifices containing mantle xenoliths on Petite-Terre Island (Mayotte, Comoros Archipelago, Western Indian Ocean) to quantifying magma fragmentation processes and eruptive dynamics. Petite-Terre explosive volcanism is the westernmost subaerial expression of a 60 km volcanic chain, whose eastern submarine tip has been the site of the 2018–2021 sub-marine eruption which saw the birth of a new volcano, Fani Maoré. The scattered recent volcanic activity and the persistence of deep seismic activity along the volcanic chain requires to constrain the origin of past activity as a proxy of possible future volcanic activity on land. Through geomorphology, stratigraphy, grain size and componentry data we show that Petite-Terre tuff rings and tuff cones are likely formed by several closely spaced eruptions forming a monogenetic volcanic complex. The eruptive sequences are composed of few, relatively thin (cm-dm) coarse and lithic rich pumice fallout layers containing abundant ballistic clasts, and fine-ash rich deposits mostly emplaced by dilute pyroclastic density current (PDCs). All deposits are dominated by vesiculated, juvenile (pumice clasts, dense clasts, and obsidian) and non-juvenile clasts from older mafic scoria cones, coral reef and the volcanic shield of Mayotte as well as mantle xenoliths. We conclude that phonolitic magma ascended directly and rapidly from the mantle and first experienced a purely magmatic fragmentation at depth (≈ 1 km deep). The fragmented pyroclasts underwent a second shallower hydromagmatic, fragmentation where they interacted with liquid water, producing fine ash and building the tuff ring and tuff cone morphologies.
... The 2018 Anak Krakatau volcano flank collapse involved a relatively small slide volume (<0.2 km 3 ) but produced a deadly tsunami affecting local coastlines due to the lack of warning (Ye et al. 2020). The post-event field survey confirmed that the maximum tsunami run-up height is 13.5 m and the maximum inundation distance is 330 m with a short tsunami period nature of 6.6 -7.4 min (Muhari et al. 2019). ...
With the advancement of the global economy, the coastal region has become heavily developed and densely populated and suffers significant damage potential considering various natural disasters, including tsunamis, as indicated by several catastrophic tsunami disasters in the 21st century. This study reviews the up-to-date tsunami research from two different viewpoints: tsunamis caused by different generation mechanisms and tsunami research applying different research approaches. For the first issue, earthquake-induced, landslide-induced, volcano eruption-induced, and meteorological tsunamis are individually reviewed, and the characteristics of each tsunami research are specified. Regarding the second issue, tsunami research using post-tsunami field surveys, numerical simulations, and laboratory experiments are discussed individually. Research outcomes from each approach are then summarized. With the extending and deepening of the understanding of tsunamis and their inherent physical insights, highly effective and precise tsunami early warning systems and countermeasures are expected for the relevant disaster protection and mitigation efforts in the coastal region.
... Letusan tersebut mengakibatkan longsoran badan gunung ke laut sehingga memicu tsunami di wilayah pesisir barat Provinsi Banten dan pesisir selatan Provinsi Lampung (Fauzi et al., 2020;Solihuddin et al., 2020). Tsunami ini menimbulkan runup maksimum 13,5m dan jarak genangan maksimum sejauh 330m (Muhari et al., 2019) Aktivitas kegempaan di sekitar Selat Sunda tercatat cukup besar. Rata-rata kejadian gempa dengan skala diatas 2,5 Skala Richter di wilayah ini mencapai 2000 kali setiap tahunnya (Naryanto, 2003). ...
Aktivitas geologis di sekitar Selat Sunda kembali mendapat perhatian melalui tsunami yang terjadi pada akhir tahun 2018. Aktivitas lainnya juga terekam melalui gempa tektonik di zona subduksi Selat Sunda dengan Magnitude 6.9 pada 2 Agustus 2019. Kondisi ini menimbulkan kekhawatiran tentang ancaman bencana gempa dan tsunami di daerah sekitarnya. Kabupaten Tanggamus yang terletak dalam radius yang cukup dekat dengan Selat Sunda memiliki dataran rendah rawan tsunami yang sangat luas khususnya pada wilayah di sekitar ujung Teluk Semangka. Berdasarkan kondisi tersebut, penelitian ini secara umum bertujuan untuk memetakan wilayah rawan tsunami, daerah layanan evakuasi untuk setiap Tempat Evakuasi Sementara (TES), dan menganalisis model aksesibilitas evakuasi. Untuk menjawab tantangan tersebut, penelitian ini dilakukan dengan mengikuti beberapa tahapan metodologi. Diawali dari penetapan wilayah studi menggunakan analisis spasial, penentuan titik TES, digitasi jaringan jalan dan mengintergasikannya dengan tools Network Analysis pada platform ArcGIS, penentuan daerah layanan evakuasi, dan memodelkan waktu tempuh dari setiap lokasi keberadaan penduduk menuju TES terdekat. Berdasarkan hasil analisis ditemukan bahwa beberapa wilayah terjauh adalah Kecamatan Semaka, Kecamatan Wonosobo dan Kecamatan Kota Agung Barat. Kecamatan tersebut memiliki waktu tempuh untuk mencapai TES lebih tinggi dari estimasi waktu kedatangan tsunami.
