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On 1 January 2024, a massive earthquake struck the Noto Peninsula in Japan, and the resulting tsunami significantly damaged the nearby coasts. This study focuses on Iida Bay, located on the peninsula that suffered severe coastal damage. We observed a tsunami waveform in Iida Bay from video analysis owing to the lack of instrument data. This, combined with the waveform observed outside the bay, was used to correct the initial sea‐surface displacements produced by a prior source model. We successfully reproduced the observed waveforms with corrected displacements and investigated how the tsunami propagated and amplified in the bay. Alongshore wave propagation and superposition were identified as crucial factors in this tsunami event. Plain Language Summary: On 1 January 2024, a large earthquake struck the Noto Peninsula in Japan, generating a tsunami that significantly impacted the nearby coasts. Post‐event surveys revealed severe damage to Iida Bay, located on the peninsula. To investigate tsunami propagation and amplification, we analyzed the images of the recorded video of the tsunami along with a numerical simulation. According to our results, the tsunami maximized during the subsequent waves rather than during the primary wave in the bay. Waves propagating along the shore developed after the primary wave of the tsunami, and some of these waves propagating from opposite sides of the bay overlapped at a specific location in the bay, where significant inundation was observed ∼20 min after the arrival of the primary wave. Key Points: Generation, propagation, and amplification characteristics of a tsunami following the 2024 Noto Peninsula Earthquake were investigatedSignificant sea‐surface displacements were concentrated in the northeastern part of the source areaWaves propagating in alongshore directions and their superposition greatly contributed to coastal damage in Iida Bay [ABSTRACT FROM AUTHOR]

On January 1 2024, at 16:10 JST, an earthquake of Mw 7.5 occurred underneath the Noto Peninsula of Ishikawa Prefecture, Japan. This event caused a cascading disaster impact on cities in the Noto Peninsula through a series of strong earthquake shakes, strong ground motions, slope failures, liquefaction, fire, and tsunamis. The tsunami first reached Suzu City a few minutes after the earthquake, eventually affecting approximately 340 km of the coast from the Ishikawa to Niigata Prefectures. The Coastal Engineering Committee of the Japan Society of Civil Engineers conducted an organized post-event field survey to understand the impact of tsunamis on land. This study summarizes the post-event field survey results and provides a general understanding of tsunami behavior and damage using measured tsunami inundation and run-up heights. [ABSTRACT FROM AUTHOR]

On January 1, 2024 at 16:10:09 JST, an Mj 7.6 earthquake struck the Noto Peninsula in the southern part of the Sea of Japan. This location has been experiencing an earthquake swarm for more than three years. Here, we provide an overview of this earthquake, focusing on the slip distribution of the mainshock and its relationship with the preceding swarm. We also reexamined the source areas of other large earthquakes that occurred around the Sea of Japan in the past and compared them with the Matsushiro earthquake swarm in central Japan from 1964 to 1968. The difference between the Matsushiro earthquake swarm and the Noto earthquake swarm is the surrounding stress field. The Matsushiro earthquake swarm was a strike-slip stress field, so the cracks in the crust were oriented vertically. This allowed fluids seeped from the depths to rise and flow out to the surface. On the other hand, the Noto area was a reverse fault stress field. Therefore, the cracks in the earth's crust were oriented horizontally. Fluids flowing underground in deep areas could not rise and spread over a wide area in the horizontal plane. This may have caused a large amount of fluid to accumulate underground, triggering a large earthquake. Although our proposed mechanism does not take into account other complex geological conditions into consideration, it may provide a simple way to explain why the Noto swarm is followed by a large earthquake while other swarms are not. [ABSTRACT FROM AUTHOR]

Predicting earthquakes through reasonable methods can significantly reduce the damage caused by secondary disasters such as tsunamis. Recently, machine learning (ML) approaches have been employed to predict laboratory earthquakes using stick-slip dynamics data obtained from sheared granular fault experiments. Here, we adopt the combined finite-discrete element method (FDEM) to simulate a two-dimensional sheared granular fault system, from which abundant fault dynamics data (i.e., displacement and velocity) during stick-slip cycles are collected at 2203 "sensor" points densely placed along and inside the gouge. We use the simulated data to train LightGBM (Light Gradient Boosting Machine) models and predict the gouge-plate friction coefficient (an indicator of stick-slips and the friction state of the fault). To optimize the data, we build the importance ranking of input features and select those with top feature importance for prediction. We then use the optimized data and their statistics for training and finally reach a LightGBM model with an acceptable prediction accuracy (R2 = 0.94). The SHAP (SHapley Additive exPlanations) values of input features are also calculated to quantify their contributions to the prediction. We show that when sufficient fault dynamics data are available, LightGBM, together with the SHAP value approach, is capable of accurately predicting the friction state of laboratory faults and can also help pinpoint the most critical input features for laboratory earthquake prediction. This work may shed light on natural earthquake prediction and open new possibilities to explore useful earthquake precursors using artificial intelligence. [ABSTRACT FROM AUTHOR]

Non‐inertial afterslip has been inferred to occur following large earthquakes. An explanation for this slow slip phenomenon is that coseismically generated stresses induce sliding on parts of a fault surface with velocity‐strengthening frictional properties. Here we develop an alternative mesoscale heuristic explanation for afterslip based on the idea that afterslip may occur on any portion of a fault that exhibits positive residual geometric moment following an earthquake, including sections that ruptured coseismically. Following a large earthquake, this model exhibits exponential time decay of afterslip and allows for variable sensitivity to coseismic event magnitude and residual geometric moment. This model provides a partial explanation for the spatial relationship of co‐ and post‐seismic slip associated with the 2011 MW = 9 Tohoku‐oki earthquake. Plain Language Summary: Afterslip is slow slip that occurs after large earthquakes. Some geodetic inferences of afterslip suggest that regions experiencing afterslip may have also slipped coeismically. This spatially coincident behavior is poorly explained by classical stress‐driven afterslip models. Here, we develop a motion‐based model to explain this possible spatial relationship. The model predicts faster afterslip rates in regions that have an excess of accumulated slip to be released following a large earthquake. This model may be used to describe the spatial relationship of co‐ and post‐seismic slip associated with the 2011 Great Japan earthquake. Key Points: We develop a geometric moment based model for time‐dependent afterslipThe model exhibits and exponential time decay of afterslip ratesThis model provides a kinematic explanation for overlapping co‐ and post‐seismic slip proximal to the 2011 great Japan earthquake [ABSTRACT FROM AUTHOR]

The structural styles and magnitudes of Alpine tectonic inversion are reviewed for the Atlantic margin of southwestern (SW) Iberia, a region known for its historical earthquakes, tsunamis and associated geohazards. Reprocessed, high-quality 2D seismic data provide new images of tectonic faults, which were mapped to a depth exceeding 10 km for the first time. A total of 26 of these faults comprise syn-rift structures accommodating vertical uplift and horizontal advection (shortening) during Alpine tectonics. At the regional scale, tectonic reactivation has been marked by (a) the exhumation of parts of the present-day continental shelf, (b) local folding and thrusting of strata at the foot of the continental slope, and (c) oversteepening of syn- and post-rift sequences near reactivated faults (e.g. "passive uplift"). This work proves, for the first time, that geometric coherence dominated the growth and linkage of the 26 offshore faults mapped in SW Iberia; therefore, they are prone to reactivate as a kinematically coherent fault network. They form 100–250 km long structures, the longest of which may generate earthquakes with a momentum magnitude (Mw) of 8.0. Tectonic inversion started in the Late Cretaceous, and its magnitude is greater close to where magmatic intrusions are identified. In contrast to previous models, this work postulates that regions in which Late Mesozoic magmatism was more intense comprise thickened, harder crust and form lateral buttresses to northwest–southeast compression. It shows these structural buttresses to have promoted the development of early stage fold-and-thrust belts – typical of convergent margins – in two distinct sectors. [ABSTRACT FROM AUTHOR]

Here we update a catalogue of 2001–2011 New Zealand earthquakes relocated with a 3-D seismic velocity model, which has recent improvements. We use P- and S-wave arrival times from earthquakes during 2001–2011 as these were manually picked with assigned quality. We demonstrate the usefulness of the catalogue by considering results from the southern South Island where GeoNet seismograph spacing is large. Later phase data used automatic picking and processing of arrival times. We relocate the 2019–2020 data from National Geohazards Monitoring Centre (NGMC) and compare seismicity patterns to consider its usefulness. We find that the auto-detected crustal earthquakes are more sparse in most of the southern South Island compared to the earlier analyst-picked data period, including Fiordland, which is one of the most seismically active areas in New Zealand. The auto-detected seismicity pattern is also problematic at greater depth and does not show a seismicity band in the lower crust across Southland evident in 2001–2011 data. The detection capability could be improved with a much denser permanent network. We recommend that the 2001–2011 relocated catalogues be used in studies of tectonics and seismic hazard across the South Island, and in studies that consider New Zealand wide seismicity patterns. [ABSTRACT FROM AUTHOR]

Coastal dikes are an essential social infrastructure to mitigate tsunami damage. However, there are no clear guidelines on effective dike shapes for reducing tsunami overflow. To examine effective dike shapes, numerical simulations of the amount of tsunami overflow at coastal dikes are conducted with reference to tsunami waveforms caused by the Great East Japan Earthquake. Results reveal the relationship between the dike shape and the amount of the overflow; the mechanism of overflow reduction based on the velocity and water level distribution is also verified. The comparison of the seaward and landward slopes of coastal dikes reveals that the seaward slope has a greater impact on the overflow, and the seaward slope with a vertical wall or a wave return structure reduces the overflow by 5%–30% compared to the 1:2 (26.6°) seaward slope. The landward slope should be determined based on the tsunami scale and the scour related to the dike stability. Since tsunami inflow damages human life and social infrastructure, achieving the overflow reduction without increasing dike height is vital. Our work contributes to rational design guidelines for coastal dikes. [ABSTRACT FROM AUTHOR]

Multi-hazard risk assessments for building portfolios exposed to earthquake shaking followed by a tsunami are usually based on empirical vulnerability models calibrated on post-event surveys of damaged buildings. The applicability of these models cannot easily be extrapolated to other regions of larger/smaller events. Moreover, the quantitative evaluation of the damages related to each of the hazard types (disaggregation) is impossible. To investigate cumulative damage on extended building portfolios, this study proposes an alternative and modular method to probabilistically integrate sets of single-hazard vulnerability models that are constantly being developed and calibrated by experts from various research fields to be used within a multi-risk context. This method is based on the proposal of state-dependent fragility functions for the triggered hazard to account for the pre-existing damage and the harmonisation of building classes and damage states through their taxonomic characterisation, which is transversal to any hazard-dependent vulnerability. This modular assemblage also allows us to separate the economic losses expected for each scenario on building portfolios subjected to cascading hazards. We demonstrate its application by assessing the economic losses expected for the residential building stock of Lima, Peru, a megacity commonly exposed to consecutive earthquake and tsunami scenarios. We show the importance of accounting for damage accumulation on extended building portfolios while observing a dependency between the earthquake magnitude and the direct economic losses derived for each hazard scenario. For the commonly exposed residential building stock of Lima exposed to both perils, we find that classical tsunami empirical fragility functions lead to underestimations of predicted losses for lower magnitudes (Mw) and large overestimations for larger Mw events in comparison to our state-dependent models and cumulative-damage method. [ABSTRACT FROM AUTHOR]

Strike-slip fault ruptures have a limited capacity to generate vertical deformation, and for this reason they are usually dismissed as potential destructive tsunami sources. At the western tip of the western Mediterranean, in the Alboran Sea, tectonics is characterized by the presence of large transcurrent fault systems and minor reverse and normal faults in a zone of diffuse deformation. The strike-slip Carboneras fault is one of the largest sources in the Alboran Sea and therefore with the greatest seismogenic capacity. It is also one of the active structures with higher slip rates in the eastern Betic fault zone and has been proposed as the source of the damaging 1522 (M 6.5; Int. VIII–IX) Almeria earthquake. The dimensions and location of the Carboneras fault imply a high seismic and tsunami threat. In this paper we present tsunami simulations from seismic sources generated with physics-based earthquake simulators. We have generated a 1 Myr synthetic seismic catalogue consistent on 773 893 events, with magnitudes ranging between Mw 3.3 and 7.6. From these events we have selected those sources producing a potential energy capable of generating a noticeable tsunami, those sources being earthquakes with magnitudes ranging from 6.71 to 7.62. The Carboneras fault has the capacity to generate locally damaging tsunamis; however, on a regional scale its tsunami threat is limited. The frequency–magnitude distribution of the generated seismic catalogue reflects the variability of magnitudes associated with the rupture of the entire fault, departing the upper limit from the classical Gutenberg–Richter potential relation. The inter-event time for the maximum earthquake magnitudes is usually between 2000 and 6000 years. The use of physics-based earthquake simulations for tsunamigenic sources allows an in-depth characterization of the scenarios, allowing a qualitative leap in their parametrization. [ABSTRACT FROM AUTHOR]

Nucleation of earthquake slip at the plate boundary fault (décollement) in subduction zones has been widely linked to the frictional properties of subducting sedimentary facies. However, recent seismological and geological observations suggest that the décollement develops in the subducting oceanic crust in the depth range of the seismogenic zone, at least in some cases. To understand the frictional properties of oceanic crustal material and their influence on seismogenesis, we performed hydrothermal friction experiments on simulated fault gouges of altered basalt, at temperatures of 100–550°C. The friction coefficient (μ) lies around 0.6 at most temperature conditions but a low μ down to 0.3 was observed at the highest temperature and lowest velocity condition. The velocity dependence of μ, (a−b), changes with increasing temperature from positive to negative at ∼100°C and from negative to positive at ∼450°C. Compared to gouges derived from sedimentary facies, the altered basalt gouge showed potentially unstable velocity weakening over a wider temperature range. Microstructural observations and microphysical interpretation infer that competition between dilatant granular flow and viscous compaction through pressure‐solution creep of albite contributed to the observed transition in (a−b). Alteration of oceanic crust during subduction produces fine grains of albite and chlorite through interactions with interstitial water, leading to reduction in its frictional strength and an increase in its seismogenic potential. Therefore, shear deformation possibly localizes within the altered oceanic crust leading to a larger potential for the nucleation of a megathrust earthquake in the depth range of the seismogenic zone. Plain Language Summary: Megathrust earthquakes in subduction zones have long been studied to mitigate damage by ground shakings and tsunamis. Frictional properties of plate boundary fault are fundamental information to understand the slip activities causing megathrust earthquakes. In this study, we focused on altered basalt, which is a rock of subducting oceanic crust and has not been focused on as much as sedimentary rocks. Laboratory friction experiments were performed at a wide temperature range with water pressurized conditions. We found that the altered basalt shows frictionally unstable behavior of the type that is prerequisite for generating an earthquake in the temperature conditions of seismogenic zone. This unstable behavior is likely to be result of alteration of oceanic crust during subduction. Because the altered basalt can be mechanically as weak as sedimentary facies, subducting oceanic crust forms an additional or perhaps even preferred candidate for sourcing megathrust earthquakes in subduction zones. Key Points: Altered basalt shows unstable frictional behavior under a wide range of hydrothermal conditionsProduction of fine‐grained albite during subduction promotes the frictional instability via pressure solution creepSubducting oceanic crust may serve as a source of nucleating megathrust earthquakes in subduction zones [ABSTRACT FROM AUTHOR]

SMPN 25 building in Padang City is a junior high school building located in the high seismic zone and prone to tsunamis. Based on the initial analysis of the existing building using the current Indonesian building codes, this building has not been able to withstand the working earthquake and tsunami loads. In this study, the retrofitting of the building was designed using concrete jacketing that is with additional dimensions and reinforcement, aimed at making the building function as a vertical evacuation structure. The structural fragility curve of the building is determined before and after retrofitting for both earthquake and tsunami loads. The fragility curve is determined from the ductility of the building for each variation of earthquake acceleration based on the Hazus standard. The first yield displacement was determined from the pushover analysis, and the ultimate displacement was determined from the time history analysis. The earthquake acceleration records used were the El-Centro earthquake, the Northridge earthquake, the Kobe earthquake, and the Padang earthquake. The results of the analysis show that the retrofit of the building structure using concrete jacketing reduces the probability of damage to the building structure due to earthquake loads by 42.06% at the level of extensive damage and by 4.42% at the level of complete damage at PGA 0.6g, while, it reduces the probability of building damage due to tsunami loads by 45.53% at the level of extensive damage and by 26.32% at the level of complete damage at a tsunami inundation depth of 4.5m. [ABSTRACT FROM AUTHOR]

The 2024 Noto Peninsula Earthquake in Japan generated tsunamis of over 3 m high in Iida Bay, causing extensive damage to ports and residential areas. The tsunamis observed in Iida Bay were remarkably higher than those at other coasts, and it can be inferred that some mechanisms may have amplified the tsunami. This study aimed to elucidate why tsunami damage was concentrated in Iida Bay. A numerical simulation showed that the tsunami energy propagating from the earthquake source fault toward Toyama Bay converged on the edge between the shallow sea (Iida Spur) and the deep sea (Toyama Trough). The concentrated tsunami energy then propagated into Iida Bay, triggering multiple secondary short-period tsunamis. According to video monitoring overlooking Iida Bay, a bore-like tsunami propagating along the coastline intersected with a tsunami directly reaching Iida Port, resulting in an over 10-m high splash when it hit the breakwater. Wavelet analysis of the computational output showed that the primary tsunami energy had an oscillation period of 5–10 min, whereas that of the secondary tsunami energy was less than 2 min. The superposition of these multiple waves most likely caused the locally amplified tsunami in Iida Bay. • Tsunamis in Iida Bay have increased for two main reasons. • Tsunami energies converged off the coast of Iida Bay due to a lens effect. • Tsunami waves were superimposed due to within-bay diffraction and reflection. • Primary and secondary tsunami periods were 5–10 min and <2 min, respectively. • The tsunami collided with a breakwater in Iida Port, creating an over 10-m high splash. [ABSTRACT FROM AUTHOR]

The January 1, 2024 Noto Peninsula M w 7.5 tsunamigenic earthquake, with at least 241 deaths, was the most destructive event in Japan following the March 2011 M w 9.0 catastrophic event. We conducted field surveys in the affected area 24 days after the event to document tsunami heights, runups, coseismic coastal uplift and damage to coastal structures. Here, we present the results of the surveys and analyze tsunami height distribution and associated damage. In our survey of 29 locations, tsunami runups and heights varied in the ranges of 4.4–6.2 m, and 1.0–4.4 m, respectively. Notably, Joetsu, the farthest location from the epicenter in our field survey, recorded the highest runup of 6.2 m, which is attributed to the directivity effect of tsunami waves. The maximum surveyed runup of 6.2 m closely aligns with the reported maximum fault slip of 4–6 m for this earthquake, confirming a long-established rule of thumb. Coastal crustal uplifts of up to 1.6 m have rendered many ports unsuitable for use. We identified three failure mechanisms affecting coastal structures: overturning caused by tsunami backwash, damage resulting from tsunami inundation currents and wave pressure, and impacts from floating objects and debris. • Maximum runup of the Jan. 2024 Noto Peninsula (Japan Sea) tsunami was 6.2 m. • Coastal crustal uplifts of up to 1.6 m have rendered many ports unsuitable for use. • Maximum tsunami runup (6.2 m) was comparable to the maximum fault slip (4–6 m). • Three failure mechanisms observed: tsunami backwash, wave pressure, debris impacts. [ABSTRACT FROM AUTHOR]

Strike-slip fault ruptures have a limited capacity to generate vertical deformation, and for this reason they are usually dismissed as potential destructive tsunami sources. At the western tip of the western Mediterranean, in the Alboran Sea, tectonics is characterized by the presence of large transcurrent fault systems and minor reverse and normal faults in a zone of diffuse deformation. The strike-slip Carboneras fault is one of the largest sources in the Alboran Sea, and therefore, with the greatest seismogenic capacity. It is also one of the active structures with higher slip rates in the Eastern Betic Fault Zone and has been proposed as source of the damaging 1522 (M6.5; Int. VIII-IX) Almeria earthquake. The dimensions and location of the Carboneras fault imply a high seismic and tsunami threat. In this paper we present tsunami simulations from seismic sources generated with physics-based earthquake simulators. We have generated a 1 Myr synthetic seismic catalogue consistent on 773,893 events with magnitudes ranging between M[sub W] 3.3 and 7.6. From these events we have selected those sources producing a potential energy capable of generating a noticeable tsunami, being earthquakes with magnitudes ranging from 6.71 to 7.62. The Carboneras Fault has the capacity to generate locally damaging tsunamis, however, on a regional scale its tsunami threat is limited. The frequency -- magnitude distribution of the generated seismic catalogue reflects the variability of magnitudes associated to the rupture of the entire fault, departing the upper limit from the classical Gutenberg-Richter potential relation showing a bell-shaped distribution. The inter-event time for the maximum earthquake magnitudes is usually j between 2000 and 6000 years. The use of physics-based earthquake simulations for tsunamigenic sources allows a robust characterization of the scenarios, allowing a qualitative leap in their parametrization. [ABSTRACT FROM AUTHOR]

Multi-hazard risk assessments for building portfolios exposed to earthquake shaking followed by a tsunami are usually based on empirical vulnerability models calibrated on post-event surveys of damaged buildings. The applicability of these models cannot easily be extrapolated to other regions of larger/smaller events. Moreover, the quantitative evaluation of the damages related to each of the hazards type (disaggregation) is impossible. To investigate cumulative damage on extended building portfolios, this study proposes an alternative and modular method to probabilistically integrate sets of single-hazard vulnerability models that are being constantly developed and calibrated by experts from various research fields to be used within a multi-risk context. This method is based on the proposal of state-dependent fragility functions for the triggered hazard to account for the pre-existing damage, and the harmonisation of building classes and damage states through their taxonomic characterization, which is transversal to any hazard-dependent vulnerability. This modular assemblage also allows us to separate the economic losses expected for each scenario on building portfolios subjected to cascading hazards. We demonstrate its application by assessing the economic losses expected for the residential building stock of Lima, Peru, a megacity commonly exposed to consecutive earthquake and tsunami scenarios. We show the importance of accounting for damage accumulation on extended building portfolios while observing a dependency between the earthquake magnitude and the losses derived for each hazard scenario. For the commonly exposed residential building stock of Lima exposed to both perils, we find that classical tsunami empirical fragility functions lead to an underestimation of predicted losses for lower magnitudes (Mw) and large overestimations for larger Mw events in comparison to our state-dependent models and cumulative damage method. [ABSTRACT FROM AUTHOR]

Chile has suffered the negative consequences of numerous large earthquakes (>MW 8.0) that generated equally large tsunamis. This paper analyses one of colonial Chile's least known earthquakes. The March 15th, 1657 earthquake destroyed the city of Conception and damaged infrastructure in the city of Santiago and rural properties between Quillota and Arauco. At the same time, it generated a major tsunami that destroyed everything in its path in Conception and the gulf of Arauco. This paper uses known and previously unknown first-hand colonial sources to describe scientifically this important seismic event, that closely resembles the recent February 27th, 2010, Maule earthquake. [ABSTRACT FROM AUTHOR]

The strong shallow earthquake with a moment magnitude (Mw) range between 6.6 and 7.0 according to different sources (AFAD, KOERI and USGS) took place at local time 14:51 on 30th October 2020, in Aegean Sea near Samos Island. According to the data given from Earthquake Department of the Disaster and Emergency Management Presidency (AFAD), the epicenter of the earthquake is 27.17 km far away from the İzmir coast and the duration of the earthquake that occurred in 14.9 km deep of the ground is 15.68 s. The main shock of the earthquake brought about a small local tsunami that struck especially Seferihisar district in Izmir and Vathi in Samos. The main shock was followed by more than 5799 aftershocks with magnitudes varying between 0.7 and 5.1 in 62 days. Turkey, Greece and the islands in Aegean Sea felt the earthquake but it caused heavy damage and casualties at Bayraklı location in the city center of Izmir due to ground effects and structural problems. According to the data released after the field investigations made by the Turkish Ministry of Environment and Urbanization in the regions affected by the earthquake, 103 buildings collapsed and urgently demolished, 700 were severely damaged, 814 were moderately damaged, 7889 were slightly damaged and 159,000 were undamaged. The earthquake and tsunami resulted in 117 deaths and 1632 injured in Turkey, whereas two deaths and several injured in Samos, despite the distance between the epicenter and Turkey coast being more than Samos Island. One of these deaths occurred as a result of the tsunami and according to official sources; it was recorded as the first person to die from a tsunami in Turkey. This study aims to examine the damage and collapses that occurred on the structures due to the earthquake and the tsunami. The types and causes of damage that occurred on both reinforced concrete (RC) and masonry structures were evaluated in detail with taking into account the conditions of the existing Turkish Building Earthquake Design Code, [TBEC, [2018] Turkish Building Earthquake Design Code. Specifications for Structures to be Built in Disaster Areas (Earthquake Department of the Disaster and Emergency Management Presidency, Ankara, Turkey).] and previous Turkish Earthquake Codes (TECs). [ABSTRACT FROM AUTHOR]

The 16 September 2015 MW8.3 Illapel Earthquake generated a tsunami that caused severe building and infrastructure damage in Coquimbo, Chile. Initial reports indicated numerous buildings, transport, energy, water and coastal protection structures sustained varying levels of damage in response to tsunami exposure. A digital 'census style' survey was carried out in Coquimbo to measure and record tsunami hazard characteristics and associated buildings and infrastructure network component damage. Flow depths measured from 655 watermarks ranged from 0.1 to 4.7 m, with a 1.47 m mean and 1.02 m standard deviation. Over 3000 damage samples were recorded for tsunami exposed buildings and infrastructure components. Damage levels for 545 buildings showed most sustained partial but repairable damage at tsunami flow depths up to 2 m. A further 2544 damage samples were collected for transport, energy, water infrastructure network components and coastal protection structures. We observed undamaged infrastructure components in high proportions and observed that complete component damage was often caused by secondary hazards (e.g. debris) or cascading impacts where seawall and stormwater culvert failures damaged co-located roads, pathways and utility poles. Future investigations of the hydrodynamic tsunami characteristics influencing infrastructure component fragility will support the analysis of physical damage to single components and cascading impacts across multiple infrastructure networks. [ABSTRACT FROM AUTHOR]

Featured Application: A 4D tomographic technique is utilized to investigate the variation of rheology around the fault zone. Although the study of spatiotemporal variation of a subsurface velocity structure is a challenging task, it can provide a description of the fault geometry as well as important information on the rheological changes caused by fault rupture. Our main objective is to investigate whether rheological changes of faults can be associated with the seismogenic process before a strong earthquake. For this purpose, a 3D tomographic technique is applied to obtain P- and S-wave velocity structures in central Taiwan using travel time data. The results show that temporal variations in the Vs structure in the source area demonstrate significant spatiotemporal variation before and after the Chi-Chi earthquake. We infer that, before the mainshock, Vs began to decrease (and Vp/Vs increased) at the hanging wall of the Chelungpu fault, which may be induced by the increasing density of microcracks and fluid. However, in the vicinity of the Chi-Chi earthquake's source area, Vs increased (and Vp/Vs decreased), which may be attributed to the closing of cracks or migration of fluid. The different physical characteristics at the junctional zone may easily generate strong earthquakes. Therefore, seismic velocity changes are found to be associated with a subsurface evolution around the source area in Taiwan. Our findings suggest that monitoring the Vp and Vs (or Vp/Vs) structures in high seismic potential zones is an important ongoing task, which may minimize the damage caused by future large earthquakes. [ABSTRACT FROM AUTHOR]

Historical catalogues show evidence for about 300 tsunamis in European coastal waters since 1600 BC, and tsunami hazard models like the NEAMTHM18 provide the probability of future inundation from earthquake-induced tsunamis. A recent wake-up call came from the 2020 Mw7.0 Samos-İzmir earthquake and the following moderate, damaging tsunami. Five accredited Tsunami Service Providers (TSPs) run by IPMA (Portugal), CENALT (France), INGV (Italy), NOA (Greece), and KOERI (Turkey), and several national centers monitor the seismicity and provide tsunami alerts in the framework of the UNESCO Tsunami Early Warning and Mitigation System in the North-eastern Atlantic, the Mediterranean and connected seas (NEAMTWS). In this paper, we focus on the state of the art of earthquake-induced tsunami risk reduction and coastal planning in Italy from the perspective of the Centro Allerta Tsunami (CAT), the INGV NTWC (National Tsunami Warning Center) and TSP. We will emphasize some limitations to draw future directions for better preparation and towards the full implementation of the tsunami warning "last-mile". [ABSTRACT FROM AUTHOR]

The 2020 Samos, M7.0 earthquake was characterized by an unusual bi-modal-type distribution of damage: limited damage in the nearfield (especially northern Samos coast) and serious localized damage in multi-story buildings in the far field (İzmir area). This pattern is not consistent with the typical distribution of isoseismal lines, and it seems not to represent an isolated effect; the 2014 Samothraki-Gökçeada M6.9 earthquake, for example, may in fact represent a parallel, though at smaller scale. For this reason, the damage pattern of the Samos earthquake may characterize historical earthquakes in the wider region, and perhaps explain, among others, some apparently large meizoseismal areas of historical earthquakes. Furthermore, the fact that damage in a part of the İzmir area occurred under moderate background acceleration has important implications for various ancient, long-period structures, especially monumental Greek and Roman multi-block columns and temples. These structures are highly resistant to seismic loads and difficult to fail under common earthquakes. However, evidence from the İzmir area indicates that, under certain conditions, common background accelerations can be highly amplified and leave their traces in such structures, for example in the Heraion temple at Samos. [ABSTRACT FROM AUTHOR]

The damage on supply and drainage water networks is a serious cause of economic disruption for urban systems affected by earthquakes. Among various concerns, the ruptures of sewer pipes and manholes generated by liquefaction determine a particularly severe sanitary hazard and require extensive, costly and time-consuming repairs. Quantitative risk assessment carried out with the characterisation and geographical mapping of seismic hazard, subsoil susceptibility, physical and functional vulnerability of the exposed elements, enables to estimate losses, identify weaknesses, inspire strategies to mitigate the impact of earthquakes and improve resilience. The present study deals with the physical vulnerability of sewer pipelines. Empirical fragility functions are derived from the evidences of liquefaction induced in Urayasu (Japan) by the 2011 Tohoku-Oki earthquake (Mw9.0). The spatial distribution of seismic signals, subsoil characteristics, pipes and surveyed damages are reconstructed in a GIS platform. An articulated methodology is developed to correlate variables and compensate their limited spatial correspondence, exploiting the complete coverage of the area with terrestrial settlements measured by LiDAR and their strong correlation with damage. Finally, ruptures of pipes are probabilistically quantified adopting a common liquefaction severity indicator as engineering demand parameter and measuring the efficiency of relations with statistical tests. [ABSTRACT FROM AUTHOR]

An unusual devastating tsunami occurred on September 28, 2018 after a strike‐slip faulting earthquake in Sulawesi, Indonesia. The induced tsunami struck Palu city with ∼4‐m flow depth. We performed two analyses to investigate the source of the tsunami. We first conducted the teleseismic source inversion and obtained the overall slip distribution of the strike‐slip fault. Our tsunami simulation from the coseismic deformation of the seismically estimated strike‐slip faulting produced a tsunami comparable to the leading part of the observation at Pantoloan. In order to reconstruct the detailed slip distribution on the fault plane, we then jointly utilized the tsunami waveform and Synthetic Aperture Radar (SAR) data. Because of the lack of SAR data in the bay, the tsunami data is necessary to constrain the offshore slip distribution, which directly induces the tsunami. The inverted source model shows a strike‐slip fault which consists of three segments extending from the epicenter to the south of 1.4°S with two bends and two asperities around Palu city. The joint inversion model accurately reconstructs the observed surface displacements and the leading part of the tsunami waveform. Our result exhibits the significant contribution of the strike‐slip faulting to the tsunami, but it also suggests additional tsunami sources, such as landslides, for the high inundations near Palu bay. The result also indicates that regional devastating tsunamis can be generated by an onshore strike‐slip fault with localized large dip slip. Plain Language Summary: The Palu, Indonesia, earthquake of September 28, 2018 produced tsunami flooding and damage in Palu city. Because of its strike‐slip mechanism, which is typically not efficient to produce tsunamis, multiple submarine landslides have been speculated as a tsunami source. We found that the fault model estimated by teleseismic waves (recorded globally outside Indonesia) can reproduce the tsunami recorded at the Pantoloan station in Palu bay. This indicates that the source of tsunami recoded at Pantoloan is mostly the fault motion due to the earthquake. We then combined the displacements measured by Synthetic Aperture Radar images and the Pantoloan tsunami waveform to estimate the detailed slip distribution on the fault. The slip model shows a strike‐slip fault with two large slip areas located near Palu city between two bends. This model well reproduces the Pantoloan tsunami but fails to fully reproduce the inundations in Palu city, suggesting that additional tsunami sources, such as landslides, should be responsible for the large inundations in Palu city. Our result suggests that a strike‐slip fault can induce a devastating local tsunami. Key Points: Two analyses utilizing teleseismic, Synthetic Aperture Radar, and tsunami data retrieve an earthquake source model that explains the observed tsunamiA strike‐slip fault with localized large dip slip of the 2018 Palu earthquake induced the devastating regional tsunamiOnshore strike‐slip faults should also be regarded as a potential source of tsunamis for regional areas [ABSTRACT FROM AUTHOR]

Community resilience analysis and performance-based tsunami design methods typically use separate fragility curves for earthquake and near-field tsunami hazards to predict damage, neglecting the direct cascading effects of the earthquake damage on the subsequent tsunami damage analysis for coastal communities. This paper presents an improved two-phase successive analysis that can incorporate the most significant sources of uncertainties in structural modeling and hazards. However, generating multi-hazard 3D fragility surfaces that fully incorporate uncertainties through Monte Carlo Simulation requires millions of successive nonlinear analyses, which can be computationally intensive. To address this issue, a multi-distributed and parallel processing architecture was used and summarized herein. This methodology has been applied to a 4-story RC building as an illustrative example and demonstrated to be highly efficient and scalable in generating near-continuous fragility surfaces for earthquake and tsunami hazards, reducing the expected computational time by over 98%. Due to their near-continuous characteristic, these surfaces are easier to implement in resilience frameworks and applications. The fragility surfaces also feature earthquake-only and tsunami-only 2D fragility curves along the intensity measure axis boundaries, making them versatile for use in resilience frameworks that focus on a single hazard or both earthquake and tsunami hazards. Therefore, the proposed method is scalable making it helpful in developing fragility models for building portfolios to be used at the community resilience modeling of full coastal cities. • A new methodology is introduced to develop earthquake-tsunami fragility surfaces that accounts for all relevant uncertainties. • Both earthquake and tsunami loadings are directly included in fragility surfaces. • These fragility surfaces are near-continuous and thus straightforward for computer implementation. • The fragility surfaces are well-suited for community-level modeling. [ABSTRACT FROM AUTHOR]

This paper describes an efficient approach to high-resolution time-reversal source imaging simulation. Dense seismograph network records are backpropagated from stations to the hypocentre through a 3-D subsurface structure model to estimate the initial source wavefield at the earthquake initiation time. By assimilating high-density observational data into the time-reversal wave propagation, a clearer source image can be determined, even for deep and distant earthquakes, than is achievable with conventional source imaging. The effectiveness of data-assimilation-based source imaging by a time-reversal wave propagation simulation with a 3-D heterogeneous structural model was demonstrated using recordings from a nationwide strong-motion seismograph network during the 2007 Off Niigata, Japan, M w 6.6 earthquake, and the 2007 Off Ibaraki, Japan, M w 6.8 earthquake. Such data-assimilated-based simulations are also effective for early forecasting of strong ground motions caused by large earthquakes through fast time-advancing simulations based on the current assimilated wavefield. We will discuss the feasibility of a disaster prevention system for the early forecasting of strong motion disasters due to large earthquakes, based on repeatedly estimating source parameters and forecasting strong motions in future time based on the current assimilated wavefields. [ABSTRACT FROM AUTHOR]

This analysis is an extension of the studies based on the space–time–magnitude domain nearest-neighborhood distances (ƞ) obtained from two successive earthquakes. We included epicentral depth as a parameter, and established a new analytical solution for seismicity clustering in the space–time–depth–magnitude domain. The proposed technique was applied to SW Japan seismic observation data for 2011–2018, and revealed that the temporal, spatial, and epicentral (T, R, E) components of the joint distribution for ƞ were prominently bimodal, indicating the presence of two, statistically distinct, earthquake populations. We used the Lomb–Scargle periodogram (LSP) to generate a power spectrum preceding the Kumamoto earthquake, and detected the periodic component of unequally spaced points for log10ƞ (logarithmic scale of ƞ). The LSP showed a dominant peak corresponding to the time period between foreshocks and aftershocks, due to the highest number of recorded ƞ observations. The technique presented in this paper can be applied globally for any time period and any seismotectonic zone preceding large earthquakes of interest. [ABSTRACT FROM AUTHOR]

Over the past decade, several long duration subduction earthquakes took place in different locations around the world such as Indonesia in 2004, China in 2008, Chile in 2010, and Japan in 2011. Long-duration and large-magnitude earthquakes are also possible to occur in the Cascadia subduction zone along the Pacific Northwest Coast of the United States. In this paper, numerical investigation was conducted to investigate the influence of earthquake duration on the structural response of steel special concentric braced frames (SCBFs). Calibration and validation of numerical models were achieved using results from recently completed shake table tests at the University of Nevada, Reno of three identical 1/2-scale one-story one-bay SCBFs under unidirectional short and long duration earthquakes. The objective of this paper is two-fold: (1) to use the experimental results to assess the suitability of current low-cycle fatigue models when incorporated into numerical models; (2) to utilize the calibrated numerical model in large number of simulations to extend and generalize the experimental results to quantify the effect of earthquake duration on SCBFs. For the latter, two suites of short and long duration ground motions were utilized to conduct incremental dynamic analysis (IDA) for the calibrated numerical models of the tested frames. The IDA, and resulting fragility curves, concluded that longer duration earthquakes result in 45% lower median displacement capacity, which could be regarded as premature low-cycle fatigue induced-failure of braces. [ABSTRACT FROM AUTHOR]

The 2018 February 6 M w 6.3 Hualien earthquake caused severe localized damage in Hualien City, located 20 km away from the epicentre. The damage was due to strong (>70 cm s−1) and sharp (duration ∼2.5 s) velocity pulses. The observed peak ground-motion velocity in Hualien City symmetrically decays with distance from the nearby Milun fault. Waveforms observed on the opposite sides of the fault show reversed polarity on the vertical and N–S components while the E–W component is almost identical. None of the published finite-fault slip models can explain the spatially highly localized large velocity pulses. In this study, we show that an M w 5.9 strike-slip subevent on the Milun fault at 2.5 km depth, rupturing from north to south at ∼0.9 V s speed, combined with site effects caused by surficial layers with low S-wave speed, can explain the velocity pulses observed at the dense strong-motion network stations. This subevent contributes only 25 per cent of the total moment of the 2018 Hualien earthquake, suggesting that a small local slip patch near a metropolis can dominate the local hazard. Our result strongly suggests that seismic hazard assessments should consider large ground-motion variabilities caused by directivity and site effects, as observed in the 2018 Hualien earthquake. [ABSTRACT FROM AUTHOR]

A strong earthquake with Mw 6.6 occurred on 20 July, 2017 in Gökova Bay at the southwest part of the Turkey, accompanied by a local tsunami which impacted Bodrum (Turkey) and Kos (Greece). This paper presents simulation of strong ground motions from this earthquake to visualize the extent of spectral acceleration over the region. A stochastic finite fault method based on a dynamic corner frequency is utilized as a simulation tool. For validation of simulation, strong motion recordings from 10 closest stations within 76 km are used. Horizontal to vertical spectral ratio and near surface attenuation parameter (kappa) of shear waves at strong motion recording stations are calculated to account for site effects. The most suitable source parameters; stress drop and pulsing area percentage are found as 2.5 MPa with 30–36% based on the residuals analyses. In general, an acceptable level of consistency is found between observed and simulated ground motions. Simulation is more successful at frequencies of 2 Hz and above. Distribution of spectral accelerations at a larger region is calculated with the best validated model parameters and compared with ground motion prediction equations. In spite of significant scatter of synthetics particularly in the near fault region, at longer epicentral distances the median values of Turkish empirical prediction better approximates the synthetics. The current results and further scenario simulations for the region are believed to complement normal faulting synthetic strong ground motion library of Turkey. [ABSTRACT FROM AUTHOR]

The 2011 Great East Japan earthquake and tsunami remind us once again that these types of cascade event can occur and cause considerable damage. The scientific community realizes the need for rapid theoretical and practical progress on cascade events to provide field teams with the necessary tools and information for action during these types of events. The earthquake damage scenario for Martinique and Guadeloupe islands (French West Indies) has already been performed within the framework of French governmental projects, but these areas, in the vicinity of the French West Indies subduction zone, are also subject to tsunami events. In this study, we propose to perform a combined scenario in which an earthquake is followed by a tsunami, as it could arrive one day, considering the seismic characteristics and potential of such a subduction zone. The vulnerability of the buildings is defined considering local specific information based on several years of field inventories and inspections and is later classified into one of the 36 model building types of HAZUS. The calculation of the damages due to tsunamis follows the HAZUS methodologies. The main novelty of our study is the calculation of damage due to the two phenomena occurring one after the other, not in parallel, as is calculated in the existing literature. Therefore, for the calculation of the damages due to the second event (i.e. the tsunami), the vulnerability characteristics of the initial structure are reduced, considering the damage state of the construction after the first event (i.e. the earthquake). Hence, in our case, this calculation approach allows us to update the number of exposed elements and their changed vulnerabilities considering the damages due to the earthquake, since certain structures are already damaged by the earthquake before the arrival of the tsunami wave. The results coming from our study and our manner of treating the cascading hazards are putting into perspective with the Hazus method for combining damages coming from earthquake and the damages coming from consequently tsunami. The results expressed as the sum of the damages in both most damaged states, Extensive and Complete, are more or less in the same range of values for both studies (our study and HAZUS 2017). However, a trend of having more percentage of complete damages (and hence, less the Extensive damages) with our method than the ones obtained with the Hazus combination can be important information for crisis managing. This is a first result for the French West Indies territory, but anyway, more studies should be carried out in order to check this trend and eventually to confirm and validate this issue for others territories with others bathymetries, vulnerabilities and seismological features. [ABSTRACT FROM AUTHOR]

The frontal part of the Japan Trench plate boundary fault, which slipped during the 2011 Tohoku‐Oki earthquake (Mw 9.0), is enriched in smectite and is intrinsically weak owing to the high swelling pressure of this mineral. Our rheometric experiments using analog fault materials demonstrate that "cohesional slip," rather than frictional slip, is a realistic faulting process in the studied fault zone. The cohesional slip can be described by the Bingham plastic model. Consequently, the coseismic shear stress is described by the yield stress and plastic viscosity. Comparison of the results with the average shear stress derived from a previous study suggests that the slip zone thickness for cohesional slip is ~1.3 cm or less. This finding is consistent with textures characterized by discrete slip planes of comparable thickness observed in the recovered fault rocks, suggesting that these slip planes were activated during the Tohoku‐Oki earthquake. Plain Language Summary: Fault behavior is commonly understood to be governed by rock frictional properties. However, this does not hold for fault zones rich in sticky clay minerals. One such example is the frontal part of the Japan Trench plate boundary fault, which slipped during the 2011 Tohoku‐Oki earthquake (Mw 9.0) and is composed of 80% smectite (a clay mineral). Our experiments indicate that this fault material can behave like a fluid during faulting. The present results, together with previous findings, suggest that faulting process in the studied fault zone is governed mostly by cohesional properties of the fault material rather than frictional. Key Points: The frontal part of Japan Trench plate boundary fault, which slipped during the 2011 Tohoku‐Oki earthquake, is composed of 80% smectiteOur experiments indicate that this material behaves like a fluid during faulting, whereby the shear stress is governed mostly by cohesionCohesional slip, rather than frictional slip, may be a realistic faulting process in this fault zone [ABSTRACT FROM AUTHOR]

On 14 May 2019, a major (Mw 7.6) earthquake struck eastern Papua New Guinea, causing a tsunami warning that was later canceled. The last major rupture in the region was a 2000 Mw 8.0 event, which resulted in massive horizontal land movements of up to several meters and a series of aftershocks with primarily thrust mechanisms, and caused a damaging tsunami. Seismic methods for characterizing the source process were applied. Vertical components of the long-period P-waves from 35 stations of the Global Seismic Network with even azimuthal coverage were adopted in the inversions. First, the focal mechanism solution was retrieved after the earthquake. From the inverted results as well as aftershock distribution, the causative fault of the great PNG earthquake was confirmed to be a fault of strike = 316°, dip = 84°, and rake = 0°, indicating that the earthquake was a left-lateral strike-slip event. Then, to clearly understand the spatiotemporal evolutionary process of the source rupture of the earthquake, far-field body wave data were collected, and the source rupture process of this earthquake was studied using the finite fault inversion method. A finite-fault model was estabished with length and width of 152 and 32 km, respectively, and we set the initial seismic source parameters referring to the center of the focal mechanism solution. This was estimated by the focal mechanism solutions of defferent studies referring to different focal mechanism solutions. We found that the focal mechanism solution determined by Global Centroid Moment Tensor Catalog was not appropriate. Inversion results indicated that the seismic moment was 3.63 × 1020 Nm (Mw 7.6), and the source duration was ~ 40 s. The rupture propagated mainly toward the northwest in an asymmetrical bilateral mode, with a maximum slip of ~ 13.2 m, and a large-scale slip patch strongly ruptured to the surface. The study of Coulomb stress changes suggested that the PNG earthquake may trigger a thrust-type rupture in the New Britain Trench, which has the potential to trigger a tsunami. [ABSTRACT FROM AUTHOR]

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Earthquakes with non‐double‐couple (NDC) components are indicators of geometric fault complexity, anisotropy, tensile failure, and fluid flow effects. NDC earthquakes have been observed in volcanic zones and interpreted as faulting related to fluid effects in the hypocentral region. In this study, we provide evidence of the occurrence of microearthquakes with NDC components in a tectonic zone. Aftershocks of the 2000 Western Tottori earthquake revealed definite NDC components based on a polarity analysis of the first P wave motion data from a hyperdense seismic observation. We modeled these events using both shear faulting with tensile failure and multiple shear ruptures. Six of the eight NDC events were well modeled by shear faults accompanied with an opening tensile crack. These results suggest that pressurized fluid or a weak tensile crack may exist along the rupture zone of the Tottori earthquake. Plain Language Summary: An earthquake is caused by a relative slip between two rock faces that breaks rocks around them. The characteristics of the source process can inform us about how the rock was deformed, which is important to deepen our understanding of earthquake generation. We studied small earthquakes in the area where a large earthquake, the 2000 Western Tottori Earthquake in Japan, occurred, using hyperdense seismic observation data. In the observations, 1,000 sensors were placed in the area, 1 km from each other. We found that small earthquakes did not only slip along the fault surfaces, but also induced an opening of tensile cracks. The opening can be explained by a local high‐pressure fluid or/and an ease of crack opening in the area. According to previous studies, both possibilities could be related to the large earthquake occurrence. Therefore, we conclude that the rock was damaged by fluid infiltration and dynamic shaking. Key Points: Microearthquakes with non‐double‐couple components in the tectonic earthquake hypocentral area were detected using P wave motion dataSix of eight non‐double‐couple events were modeled by shear fault with tensile crack, and two remaining events by multiple shear ruptures [ABSTRACT FROM AUTHOR]

Following the Great East Japan Earthquake, a massive tsunami caused serious damage to coastal dikes. Local scour at the ground behind these dikes reportedly causes dike failures. It is important to reveal the scour process to establish methods for effective scour countermeasures. Herein, we focus on geogrids. To verify this proposal and examine its design, flume-model experiments were performed for non-liquefied and liquefied grounds behind coastal dikes. The results showed that the scour amount and area were reduced drastically when geogrids were present. Geogrids on the sand-bed surface changed the direction of overflow water. Thus, a scour hole developed away from a coastal dike model. Furthermore, geogrids exerted a scour-reduction effect even during liquefaction. [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]

• Changes in time preferences induced by tsunami in the Great East Japan Earthquake. • Study uses panel survey data before and after the earthquake. • Employs the (β, δ) model to capture individuals' time preferences. • Increased present bias (smaller β) and insignificant change in time discount factor (δ). • This change persists even five years after the earthquake. This study examines whether individuals' time preferences are affected by the damage caused by the tsunami resulting from the Great East Japan Earthquake of 2011 using panel surveys before and after the earthquake. When the change in time preferences is measured using the (β, δ) model, present bias tendency increases (shrinking β), although there is no statistically significant change in the time discount factor (δ) for those affected by the tsunami. The hyperbolic discounting dummy also shows an increase in time inconsistency. This change persists even five years after the earthquake. [ABSTRACT FROM AUTHOR]

It is necessary to identify the role and limitation of a tsunami protection facility in installing the hardware elements and performing damage-reduction activities necessary to mitigate aftermath of the calamity. This paper examines the probabilities of occurrence of earthquakes of various magnitudes based on the earthquake occurrence frequency, estimates the corresponding tsunami damage, and proposes a method to determine the expected damage reduction, B(H), and expected damage, D(H), when a tsunami protection facility of a given scale, H, is built. With the goal of facilitating an agreement with the local government regarding the scale of the tsunami protection facility, promoting damage reduction measures, and reducing the overall social cost, it also proposes a scheme built on the results of the aforementioned method and the cost, C(H). The present method can also be used to identify residual risks, which will allow concerned parties to set concrete damage reduction targets. [ABSTRACT FROM AUTHOR]

Abstract The 2016 Mw 7.8 Kaikoura earthquake and consequent tsunami have been controversial because of uncertainty over whether and where the plate interface ruptured and the incapability of the proposed source models to reproduce the near-field runup of 7 m. Existing models identify a wide range of locations for the interface rupture, from on land to offshore, and fail to reproduce runup of 7 m near Kaikoura. To generate the large tsunami peak in Kaikoura tide gauge record and the observed runup height, offshore seafloor movement is necessary, but the offshore extension of the plate-interface rupture and its type, either seismic rupture or a landslide, is uncertain. Here, we propose a submarine landslide in addition to the earthquake source, with the landslide delayed 10–20 min after the earthquake rupture. The landslide volume is 4.5–5.2 km3, located within 173.7–174.3oE (longitude) and 42.6–42.15oS (latitude). Our proposed dual tsunami source successfully reproduces near-field tide gauge records as well as observed near-field runup height of 7 m. We showed that more accurate source models of earthquakes can be achieved by considering observed runup data through runup inversions in addition to waveform inversions. [ABSTRACT FROM AUTHOR]

Chile has a long history of earthquakes and tsunamis, and as a result the country has implemented a strict regulatory system that has enabled adequate responses in the case of recent earthquakes. However, responses to tsunami events are still in a developmental stage, especially after the earthquake and tsunami of 2010. In this sense, the city of Iquique presents a serious challenge with regard to tsunami, as it could suffer severe, extensive damage caused by flooding of 5-10 meters. Moreover, in many places the distance between the shore and safe areas on higher ground is excessive, thereby causing serious risk for the population. This article examines Iquique and its potential tsunami scenarios by identifying and pinpointing the weaknesses in its urban safety network. Finally, possible improvements to the existing system are explored from an architectural design viewpoint, specifically through the incorporation of a system of vertical evacuation structures. [ABSTRACT FROM AUTHOR]

Investigating spatio-temporal changes in crustal structure is a key to understanding the dynamic processes in the earth's crust associated with large earthquakes and volcanic activities. The dense seismic network in the northeast part of Japan (Tohoku region) allows us to apply seismic interferometry to continuous records of ambient noise data for studying crustal changes related to the 2008 M w 6.9 Iwate-Miyagi Nairiku earthquake and the 2011 M w 9.0 Tohoku-oki earthquake. We track changes in both seismic scattering properties and velocities over five years and spatially localize them based on the coda wave decorrelation and travel time sensitivity kernels calculated from the solution of the radiative transfer equation. The 2008 Iwate-Miyagi Nairiku earthquake caused significant changes in both seismic scattering properties and seismic velocities in the vicinity of the epicenter subjected to dynamic or/and static stress perturbations. Changes in scattering properties associated with the 2011 Tohoku-Oki earthquake around some active volcanoes in the Tohoku region are likely related to geofluid migrations triggered by strong vibrations during the large earthquake. The decrease in seismic velocity exists mainly along the eastern coastal region and extends to the central Quaternary volcanic chains under the combined dynamic and static stress changes by the earthquake. The waveform correlation is possibly sensitive to the fluid content and might be a useful indicator of fluid migration in the crust. This is the first comprehensive demonstration and comparison of the spatio-temporal changes of seismic scattering properties and velocities at long-term and regional scales under the influence of two large earthquakes. • Large earthquakes caused changes in subsurface structure in northeastern Japan. • Fluid migration causes co-seismic changes in scattering properties near volcanoes. • Both dynamic and static stress affect co-seismic velocity drops. [ABSTRACT FROM AUTHOR]

The article presents the discussion on telecommunication cables on the seafloor monitoring seismic activity. Topics include rapid earthquake detection, early warning of damaging ground shaking, and tsunami prediction and verification; and implementation of an array of cable sensing technologies for geophysical monitoring.

Earthquakes and tsunami disasters happen suddenly, devastating cities in just a few minutes. For decision makers to manage such disasters, they need current information on the status of their cities, but all information is collected separately and on paper now. All disaster-related information should be integrated to support decision making. To develop such an integrated system, Peru and Japan launched a new SATREPS project, "Development of Integrated Expert System for Estimation and Observation of Damage Level of Infrastructure in Lima Metropolitan Area," in 2021. The project consists of four groups. Group 1 is related to earthquake and tsunami hazards, estimating the level of shaking and predicting the damage due to tsunami. Group 2 is related to damage detection/estimation, using sensing devices to estimate the level of damage to buildings and other infrastructure. Group 3 is related to understanding the damage over a wide area through satellite images, and also to the integration of all information from Groups 1 to 3. Group 4 is related to developing the capacity to utilize the integrated expert system. This special issue has been organized to present the progress accomplished in the first two years and to share the project's achievements. It covers the fields of earthquake hazards, building and infrastructure damage estimation, damage estimation with satellite imagery, and human loss estimation. [ABSTRACT FROM AUTHOR]