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The Hunga Tonga–Hunga Ha’apai (HTHH) volcanic eruption in January 2022 generated catastrophic tsunami and contends for the largest natural explosion in more than a century. The main island, Tongatapu, suffered waves up to 17 m, and Tofua Island suffered waves up to 45 m, comfortably placing HTHH in the “megatsunami” league. We present a tsunami simulation of the Tongan Archipelago calibrated by field observations, drone, and satellite data. Our simulation emphasizes how the complex shallow bathymetry of the area acted as a low-velocity wave trap, capturing tsunami for more than 1 hour. Despite its size and long duration, few lives were lost. Simulation suggests that HTHH’s location relative to urban centers saved Tonga from a worse outcome. Whereas 2022 seems to have been a lucky escape, other oceanic volcanoes have the capacity to spawn future tsunami at HTHH scale. Our simulation amplifies the state of understanding of volcanic explosion tsunami and provides a framework for assessment of future hazards.

In mountainous areas during intese rain events shallow landslides are often triggered adding their effect and enhancing the damaging consequences of flash flood. Many coastal area of the Mediterranean are exposed to such events, as recently largely happened in Italy, France, Spain and Greek. Large portions of the coastline mountainous territories have been settled and modified since ancient times with agricultural terraces, in order to practice the subsitence cultivation. This kind of anthropogenic modification of the slopes may be considered as an artificial immobi-lization of debris cover along steep slopes and, particularly after their abandonment, they can turn into sources of shallow landslides. Then terraces from belonging to soil and water conservation measures may represent a source of hazard if not properly mainteined. Considering the intense rain event that hit the Portofino promontory in 1915 causing strong damage to the Medieval monk Abbey in the iconic small San Fruttuoso village in northern Italy, a numerical modeling has been applied basing on historical testifying and the available evidences. A possible terraced area has been highlighted as a source area for the debris/mud flow that hit the Abbey andthe model has been applied to assess its effect. This reconstruction allows to test the modeling technique in order to furtherly assess possible risk scenario even in other areas and in the framework of the H2020 RECONECT project, where recovering ancient terraces is considered in the framework of the Nature Based Solutions to riduce geo-hydrological risk.

A hazard assessment of submarine landslide-generated tsunami for the east Australian continental slope between Jervis Bay and Fraser Island is presented. Submarine landslides are present in water depths of approximately 400 to 3500 m along the entire length of continental margin, but are increasingly prevalent northward of Coffs Harbour without clustering at any particular water depth. Two hundred sixty individual submarine landslide scars that are greater than 1 km in width have been identified. Of these, 36 have been calculated to produce a tsunami flow depth equal to or greater than 5 m at the coastline for an assumed landslide downslope velocity of 20 ms−1. Landslides that are both thick (> 100 m) and wide (> 5 km) have the greatest potential to generate the largest coastal flow depths (> 10 m). The water depth of a landslide’s centre of mass strongly influences the onshore height of the tsunami’s surge with the larger events generated in shallower water depths (~ 500–1500 m). The maximum flow depth at the coastline is larger for thicker (50–250+ m) canyon landslides which occur on steeper slopes (> 4°), compared to thinner (

The frequent occurrence of landslide tsunami has aroused great social concern, hence an efficient approach for modeling the phenomena is required urgently. Herein, we present and supplement a meshless numerical model named ‘Tsunami Squares’ (TS). TS simulates both the landslide and its generated wave using an updated numerical scheme that has enhanced computational efficiency. TS also provides an artful way of approximating linear dispersive wave propagation and non-linear wave inundation that makes it quite capable of simulating real-scale events. A well-designed test that compares TS output with an analytical formula for a tsunami propagation calculation provides firm validation of the approach. We then applied the ‘Tsunami Squares’ to simulate the 1792 Unzen-Mayuyama mega slide and generated tsunami. This event remains the largest volcanic disaster in the history of Japan. Landslide dynamics simulated by TS coincide with historical reports and the known geometry of landslide deposits. The model output of tsunami runup heights well match the observed values recorded by the locations of historical ‘Tsunami Stones’. This well documented and data-rich case further validates the ‘Tsunami Squares’ model and the excellent reproduction of the 1792 event provides new insights for better understanding of landslide tsunami hazards.

Subaerial landslides falling into confined water bodies often generate impulsive waves. Damaging landslide tsunamis in Three Gorges Reservoir, China, have struck several times in the last 15 years. On June 24, 2015, a 23 × 104 m3 slope failure occurred on the east bank of the Daning River opposite Wushan Town. The sliding mass intruded into the Three Gorges Reservoir and initiated a reservoir tsunami that resulted in two deaths and significant damage to shipping facilities. A post-event survey revealed the landslide geometry and wave run-up distribution, while an eyewitness video captured most of the landslide motion. Employing these firm constraints, we applied the Tsunami Squares method to simulate the 2015 Hongyanzi landslide and tsunami. The simulation revealed that the landslide experienced a progressive failure in the first few seconds and impacted the water with a maximum velocity of ~ 16 m/s. The initial wave propagated to the opposite shore in an arch shape, and the water surface reached a maximum amplitude of ~ 11 m near the landslide. Wave amplitude-time curves at four points on the river cross section show that the initial wave reached Wushan town in about 50 s with an average wave velocity of ~ 30 m/s. The maximum wave run-ups on the shoreline opposite the landslide are around 6 m and attenuate to less than 1 m beyond 2-km distance. The landslide simulation matches the observed geological profile and the eyewitness video, and the numerical results coincide with the observed wave run-up heights. Nearly 80% of landslide energy is lost due to frictional resistances, but the remaining fraction imparted to the tsunami carried catastrophic consequences to a large region. The numerical results emphasize the efficiency and accuracy of Tsunami Squares method for a “Quick Look” simulation of a potential landslide.

Large subduction zone earthquakes often cause tsunamis, but observational data for hazard analysis is limited. Synthetic catalogs of seismically-generated tsunami scenarios can be created by pairing earthquake and wave simulations. Tsunami Squares is one such wave simulator, explicitly tracking water mass and momentum, allowing simulation of dry land and the inundation process. We demonstrate a C++ port of Tsunami Squares paired with the Virtual Quake simulator by replicating the 2011 Great East Japan Earthquake and Tsunami. Comparisons of coastal run-up and wave heights with observations finds good agreement, with future improvements coming from tsunami source time dependence. Keywords: Tsunami Squares, Simulation, Hazard analysis

Tsunami events in antiquity had a profound influence on coastal societies. Six thousand years of historical records and geological data show that tsunamis are a common phenomenon affecting the eastern Mediterranean coastline. However, the possible impact of older tsunamis on prehistoric societies has not been investigated. Here we report, based on optically stimulated luminescence chronology, the earliest documented Holocene tsunami event, between 9.91 to 9.29 ka (kilo-annum), from the eastern Mediterranean at Dor, Israel. Tsunami debris from the early Neolithic is composed of marine sand embedded within fresh-brackish wetland deposits. Global and local sea-level curves for the period, 9.91–9.29 ka, as well as surface elevation reconstructions, show that the tsunami had a run-up of at least ~16 m and traveled between 3.5 to 1.5 km inland from the palaeo-coastline. Submerged slump scars on the continental slope, 16 km west of Dor, point to the nearby “Dor-complex” as a likely cause. The near absence of Pre-Pottery Neolithic A-B archaeological sites (11.70–9.80 cal. ka) suggest these sites were removed by the tsunami, whereas younger, late Pre-Pottery Neolithic B-C (9.25–8.35 cal. ka) and later Pottery-Neolithic sites (8.25–7.80 cal. ka) indicate resettlement following the event. The large run-up of this event highlights the disruptive impact of tsunamis on past societies along the Levantine coast.

Landslide tsunami generation is a complex physical process that involves solid materials interacting with water bodies and other 3D nonlinear wave effects. Modeling of this process ranks as an urgent task because wave source features are crucial clues for subsequent tsunami motions and hazards threatening coastlines. Herein, we introduce a concept of ‘Push Ahead’ (PA) in landslide/water interactions and propose a PA formulation integrated in a meshless numerical procedure named ‘Tsunami Squares’ (TS) for modeling of landslide tsunami generation. We draw comparisons on the physical significances of PA acceleration versus ‘Drag Along’ (DA) acceleration and conventional aerodynamic and hydrodynamic solutions. We carry out physical experiments of wave generation by block-dragging and gravel flows and corresponding TS simulations to study PA effects in landslide/water interactions. Wave features in TS simulations match the experimental observations in a reasonable range, providing a firm validation of the PA formulation in the TS approach. Sensitivity analysis that compares simulations with various ratios of PA acceleration is carried out both for the block-dragging and gravel flow experiments. The comparisons indicate that PA acceleration plays an important role in landslide wave generation and that larger PA accelerations make greater contributions to the initial wave source. We discuss intrinsic relations between PA formulation and the empirical equations derived from previous experiment studies that support the validity and applicability of the PA solution. We also insist that the complex 3D wave effects such as dispersion, shoaling, refraction, reflection and superposition, occurring in the experiments can be well reproduced in the TS simulations. The newly proposed PA acceleration that works together with our previously presented ‘Drag Along’ and ‘Lift Up’ effects can excellently illustrate the mechanical process of landslide water interactions. We conclude that TS simulations that do not include the ‘Push Ahead’ acceleration can seriously underestimate landslide tsunami size.

Landslide tsunami in reservoirs can inflict serious consequences and they have aroused social concern worldwide. Herein, we introduce a historical reservoir tsunami that occurred on June 2007 in Shuibuya Reservoir, China. After a progressive failure over 20 days, the Dayantang slope with a volume of 3 million cubic meters slid into the Shuibuya Reservoir and spawned a giant tsunami that ran up ~50 m on the opposite shoreline and caused disastrous consequences. To model the 2007 tsunami, we apply a meshless numerical approach called ‘Tsunami Squares’ (TS) that takes into account the landslide/water interactions. TS simulates both the landslide and its generated tsunami and introduces ‘Push Ahead’ (PA) and ‘Drag Along’ (DA) accelerations to mimic the physical mechanics in the process. The accuracy and efficiency of TS method are verified by a well-designed landslide tsunami experiment that compares the observed wave dynamics with the ones simulated by TS and achieves an excellent match between the two. Landslide simulations indicate a maximum impact velocity of ~20 m/s and that the computed post-slide mass stopped on the near river bed with a shape coinciding with the field observations. Wave simulations present a large region of wave impacts and a maximum wave runup height of 52.9 m at the opposite bank facing the landslide scarp that is comparable to the observation (~50 m). Sensitivity analysis that compares the simulations with, and without, PA and DA accelerations is carried out both for the experimental wave and the 2007 one. This comparison indicates that TS simulations that do not include PA and DA can seriously underestimate landslide tsunami size.

On December 4, 2007, a three million cubic metres landslide impacted Chehalis Lake, 80 km east of Vancouver, Canada. The failed mass rushed into the lake and parented a tsunami that ran up 38 m on the opposite shore, destroyed trees, roads and campsite facilities. Armed with field surveys and multihigh-tech observations from SONAR, LiDAR and orthophotographs, we apply the newly developed ‘Tsunami Squares’ method to simulate the Chehalis Lake landslide and its generated tsunami. The landslide simulation shows a progressive failure, flow speeds up to ∼60 m s–1, and a slide mass stoppage with uniform repose angle on the lakebed. Tsunami products suggest that landslide velocity and spatial scale influence the initial wave size, while wave energy decay and inundation heights are affected by a combination of distance to the landslide, bathymetry and shoreline orientation relative to the wave direction.

We have developed a new method, named “Tsunami Squares”, for modeling of landslides and landslide-generated waves. The approach has the advantages of the previous “Tsunami Ball” method, for example, separate, special treatment for dry and wet cells is not needed, but obviates the use of millions of individual particles. Simulations now can be expanded to spatial scales not previously possible. The new method accelerates and transports “squares” of material that are fractured into new squares in such a way as to conserve volume and linear momentum. The simulation first generates landslide motion as constrained by direct observation. It then computes induced water waves, given assumptions about energy and momentum transfer. We demonstrated and validated the Tsunami Squares method by modeling the 2008 Three Gorges Reservoir Gongjiafang landslide and river tsunami. The landslide’s progressive failure, the wave generated, and its subsequent propagation and run-up are well reproduced. On a laptop computer Tsunami Square simulations flexibly handle a wide variety of waves and flows, and are excellent techniques for risk estimation.

Three commercial bis-benzoxazine monomers based on the aniline derivatives of bisphenol A (BA-a), bisphenol F (BF-a), and 3,3-thiodiphenol (BT-a) are examined using a variety of spectroscopic, chromatographic, and thermomechanical techniques. The kinetics of the polymerization of BA-a were found to be well described using an autocatalytic model for which values of n = 1.39 and m = 2.49 were obtained for the early and later stages of reaction respectively (activation energy = 81-88 kJ/mol.). Following recrystallization the same monomer yielded values of n = 1.80, m = 0.92, and Ea = 94-97 kJ/mol. BF-a and BT-a were also found to be well described using an autocatalytic model for which values of n = m = 2.11 (BF-a) and n = 2.10, m = 1.47 (BT-a) were obtained for the early and later stages of reaction (activation energy = 80-84 kJ/mol. for BF-a and 88-95 kJ/mol. for BT-a). The kinetic data are compared with parallel studies involving chemically initiated benzoxazine monomers. Molecular simulation is used to examine the rotational freedom of the central bridging units and this is related to the degree of conversion achieved. © 2014 Wiley Periodicals, Inc.

2,2-Bis(3,4-dihydro-3-phenyl-2H-1,3-benzoxazine)propane (BA-a) is blended with oligomers of polyarylsulfone (PSU) and polyarylethersulfone (PES) of different low/intermediate molecular weights (3000–12 000 g mol–1) and terminal functionality (chloro-, hydroxyl- or benzoxazinyl- (Bz)). Fracture toughness (KIC) is observed to increase from 0.8 MPa m0.5 for cured BA-a to 1 MPa m0.5 with the incorporation of 10 wt % PSU-Bz (12 000 g mol–1). Generally, greater improvements in KIC are observed for the PES oligomers compared with the PSU oligomers of equivalent molecular weight. The terminal functionality of the thermoplastic has a lesser effect on improving toughness than increasing the molecular weight or the nature of the polymer backbone. Surface analysis of the fractured surfaces show greater phase separation and crack pinning in the PES toughened system. Where crack pinning is less obvious, as in the case of hydroxyl-terminated PES (of 6000 g mol–1), this coincides with a drop in fracture toughness.

We investigate an early nineteenth‐century earthquake that has been previously cataloged but not previously investigated in detail or recognized as a significant event. The earthquake struck at approximately 4:30 a.m. LT on 8 January 1817 and was widely felt throughout the southeastern and mid‐Atlantic United States. Around 11:00 a.m. the same day, an eyewitness described a 12‐inch tide that rose abruptly and agitated boats on the Delaware River near Philadelphia. We show that the timing of this tide is consistent with the predicted travel time for a tsunami generated by an offshore earthquake 6–7 hours earlier. By combining constraints provided by the shaking intensity distribution and the tsunami observation, we conclude that the 1817 earthquake had a magnitude of low‐ to mid‐ M 7 and a location 800–1000 km offshore of South Carolina. Our results suggest that poorly understood offshore source zones might represent a previously unrecognized hazard to the southern and mid‐Atlantic coast. Both observational and modeling results indicate that potential tsunami hazard within Delaware Bay merits consideration: the simple geometry of the bay appears to catch and focus tsunami waves. Our preferred location for the 1817 earthquake is along a diffuse northeast‐trending zone defined by instrumentally recorded and historical earthquakes. The seismotectonic framework for this region remains enigmatic.

Three bis-benzoxazine monomers based on the aniline derivatives of bisphenol A (BA-a), bisphenol F (BF-a), and 3,3'-thiodiphenol (BT-a) are examined using a variety of spectroscopic, chromatographic, and thermomechanical techniques. The effect on the polymerization of the monomers is compared using two common compounds, 3,3'-thiodiphenol (TDP) and 3,3'-thiodipropionic acid (TDA), at a variety of loadings. It is found that the diacid has a greater effect on reducing the onset of polymerization and increasing cross-link density and T g for a given benzoxazine. However, the addition of >5 wt % of the diacid had a detrimental effect on the cross-link density, T g, and thermal stability of the polymer. The kinetics of the polymerization of BA-a were found to be well described using an autocatalytic model for which values of n = 1.64 and m = 2.31 were obtained for the early and later stages of reaction (activation energy = 81 kJ/mol). Following recrystallization the same monomer yielded values n = 1.89, m = 0.89, and E a = 94 kJ/mol (confirming the influence of higher oligomers on reactivity). The choice of additive (in particular the magnitude of its pK a) appears to influence the nature of the network formation from a linear toward a more clusterlike growth mechanism.

Online Material: Supplemental figures of space‐time and frequency‐magnitude relations, scaling plots, mean and covariance plots of interevent times, probability distribution functions of recurrence intervals, and earthquake density plots. In order to understand earthquake hazards we would ideally have a statistical description of earthquakes for tens of thousands of years. Unfortunately the ∼100‐year instrumental, several 100‐year historical, and few 1000‐year paleoseismological records are woefully inadequate to provide a statistically significant record. Physics‐based earthquake simulators can generate arbitrarily long histories of earthquakes; thus they can provide a statistically meaningful history of simulated earthquakes. The question is, how realistic are these simulated histories? This purpose of this paper is to begin to answer that question. We compare the results between different simulators and with information that is known from the limited instrumental, historic, and paleoseismological data. As expected, the results from all the simulators show that the observational record is too short to properly represent the system behavior; therefore, although tests of the simulators against the limited observations are necessary, they are not a sufficient test of the simulators’ realism. The simulators appear to pass this necessary test. In addition, the physics‐based simulators show similar behavior even though there are large differences in the methodology. This suggests that they represent realistic behavior. Different assumptions concerning the constitutive properties of the faults do result in enhanced capabilities of some simulators. However, it appears that the similar behavior of the different simulators may result from the fault‐system geometry, slip rates, and assumed strength drops, along with the shared physics of stress transfer. This paper describes the results of running four earthquake simulators that are described elsewhere in …

We apply the recently developed «tsunami ball» method to construct a physics-based simulation of the 1963 Vaiont Reservoir landslide and flood disaster. Previous tsunami ball applications restricted attention to landslide-generated sea waves and local runup. For the first time, we expand the approach to include overland flows and floods in a dam-break like situation. The Vaiont landslide was not a debris avalanche, but rather a semi-coherent slump. The slump versus avalanche distinction is embodied with a 2-D variation of a particulate landslide model. With proper adjustment of landslide parameters, we find that a slump of dimension and volume consistent with observations can indeed slip from the south slope of the reservoir, splash water ∼200 m up on the north slope, spill 30 million m3 of water over the dam and flood the valley below – all as were recorded in that day’s events. Incorporating runup and flood information with geological data provides additional insight into the kinematics of the landslide. The observed distribution of inundation requires that the eastern part of the landslide begin to move before the western part, so trapping and pushing more water over the dam than would otherwise have been the case. As aids for visualization, this paper includes links to Quicktime movies of the simulations, including a three dimensional «fly by».

Many analyses of tsunami generation and inundation solve equations of continuity and momentum on fixed finite difference/finite element meshes. We develop a new approach that uses a momentum equation to accelerate bits or balls of water over variable depth topography. The thickness of the water column at any point equals the volume density of balls there. The new approach has several advantages over traditional methods: (1) by tracking water balls of fixed volume, the continuity equation is satisfied automatically and the advection term in the momentum equation becomes unnecessary. (2) The procedure is meshless in the finite difference/finite element sense. (3) Tsunami balls care little if they find themselves in the ocean or inundating land. We demonstrate and validate the tsunami ball method by simulating the 1958 Lituya Bay landslide and tsunami. We find that a rockslide of dimension and volume (3 - 6 × 107m3) generally consistent with observations can indeed tumble from 200–900 m height on the east slope of Gilbert Inlet, splash water up to ~ 500 m on the western slope, and make an impressive tsunami running down the length of the fiord. A closer examination of eyewitness accounts and trimline maps, however, finds a "rockslide only" tsunami somewhat lacking in size outside of Gilbert Inlet. This discrepancy, coupled with fact that ~ 3 × 108m3of sediment infilled the deepest parts of Lituya Bay between 1926 and 1959, suggests that the source of the 1958 tsunami was not one landslide, but two. The initial rockslide generated the famous big splash and cratered the floor in front of Lituya Glacier. We propose that the impact of the rockslide destabilized the foundation of the Glacier and triggered a second larger, but slower moving subglacier slide. The subglacier slide induced the fresh normal faults on the collapsed glacier above, helped to bulk up the rockslide tsunami outside of Gilbert Inlet, and supplied most of the infill evident in post-1958 bathymetric charts.

Summary. This note presents an exact analytical formula for determining the magnitude of coseismic surface volume change (δV) of earthquake faults in a half-space. For a Poisson solid, the formula is remarkably simple; δV=Mzz|8μ, where Mzz is one of the moment tensor elements of the source. Maximum δV values derive from dip slip on faults plunging 45°. For these events, surface volume changes of 0.0001 and 4.3 km3 can be expected for magnitude 5 and 8 earthquakes respectively. All of the coseismic surface volume change is recovered in the interseismic period through relaxation of the Earth and rebound of the surface. A useful rule of thumb for estimating the magnitude of vertical rebound in 45° dip slip events is δhp=Δs/24, where Δs is the coseismic slip on the fault.

Seismic sea waves in the eastern Mediterranean have been reported since written history first emerged several thousand years ago. We collected and investigated these ancient and modern reports to understand and model the typical tsunamigenic sources, with the ultimate purpose of characterizing tsunami hazard along the Levant coasts. Surprisingly, only 35% of the tsunami reports could be traced back to primary sources, with the balance remaining questionable. The tsunamis varied in size, from barely noticeable to greatly damaging, and their effects ranged from local to regional. Overall, we list 21 reliably reported tsunamis that occurred since the mid second century b.c. along the Levant coast, along with 57 significant historical earthquakes that originated from the “local” continental Dead Sea Transform (dst) system. An in-depth evaluation shows that 10 tsunamis are clearly associated with on-land dst earthquakes, and therefore, as formerly suggested, they probably originated from offshore, seismogenically induced slumps. Eight tsunamis arrived from the “remote” Hellenic and Cypriot Arcs, one from Italy, and two are left with as yet unrecognized sources. A major conclusion from this work is that onshore earthquakes commonly produce tsunamis along the Levant coastline, and that analogous situations are present elsewhere in the Mediterranean, as well as along the California coast and in another regions with active faults near the coast. We modeled three typical scenarios, and in light of the Sumatra experience, we examined the more likely severe magnitudes. This of course leads us toward the upper range of expected run-ups. The models show that sooner than five minutes after a strong earthquake produces an offshore slump, which occurs after close to a third of the large dst earthquakes, a 4- to 6-m run-up may flood part of the Syrian, Lebanese, and Israeli coasts. Tsunamis from remote earthquakes, however, arrive later and produce only 1- to 3-m run-ups, but are more regional in extent. Online material: Tsunami modeling and reports.

From the outset, the vision of the Regional Earthquake Likelihood Models (RELM) project recognized that the best way to come to grips with the full impact and uncertainty in earthquake hazard estimates is to compare a wide range of independent, well-documented, and physically defensible hazard models that produce identically formatted output. Ideally, these models should be rooted in the complete spectrum of geophysical input. Toward this end, I offer testable earthquake potential maps based on geodesy, geology, historical seismicity, and computer simulations of earthquakes. Motivation. Until recently, earthquake rate estimation was entirely the domain of geologists and seismologists. With well-defined faults and sufficiently frequent earthquakes, geology, historical seismicity, and paleoseismology can furnish fairly reliable earthquake statistics. More commonly, questionable fault geometries, fault slip rates, fault rupture modes, and scattered seismicity characterize the situation, and earthquake statistics do not reveal themselves readily. For much of the world, historical seismicity and paleoseismology cannot constrain earthquake statistics to the degree necessary for an acceptable rate assessment. Today, information from space geodesy patches some of these voids. Space geodetic monitoring quantifies potential earthquake activity within a network even if that activity occurs on faults that are unknown, too slowly slipping, or too deep to study by conventional geological or seismological techniques. Geodesy's most valuable contributions in this arena spring from its ability to: Technical description. Geodetic earthquake potential maps require few inputs. This feature is both the beauty and the value of the approach. The steps in computing the maps include: 1. Compile a GPS velocity map for …

SUMMARY We construct a new class of granular landslide models in which avalanches are simulated with large numbers of independent particles moving under the influence of topographically derived gravitational and centripetal acceleration. Concurrently, the particles suffer deceleration due to basal and dynamic friction. The novel aspect of the calculation is that complex particle-toparticle interactions, fluctuating basal contacts, and unresolved topographic roughness within and below the deforming flow are mimicked by random perturbations in along-track and cross-slope acceleration. We apply the method to the 1980 May 18 Mount Saint Helens debris avalanche by constraining the initial geometry and structure of the slide mass from geological data, and the initial failure sequence from eyewitness accounts. After tuning coefficients of mechanical friction and random accelerations, the landslide simulation generates a final deposit whose extent, thickness, morphological structure and lithological variation closely replicate those observed. Moreover, the model avalanche is consistent kinematically with mapped patterns of bedrock scouring, deposit superelevation, and net force history implied from seismic records. To be successful, the slide mass must be divided into upper, high-friction and lower, low-friction members. This division corresponds to fresh, water-unsaturated and hydrothermally altered, water-saturated rock units and points to a mechanical explanation of the kinematics of the debris avalanche. Success in reproducing many features of the Mount Saint Helens avalanche indicates that debris-deposit data may be used to determine the kinematic histories of less well-observed landslides.

In this article, we assess the human and economic hazard posed by tsunami waves generated from impacts of sub-2 km diameter asteroids. Annually, on average, 182(+197/−123) people will be affected by impact-induced waves with a corresponding infrastructure loss of $18(+20/−12)M/y. Half of the tsunami hazard stems from impactors with diameters less than 300 m. One near Earth asteroid will survive atmospheric transit and strike somewhere into Earth’s oceans every 5880 years, on average. In the mean generic scenario, the tsunami from the impact affects 1.1 million people and destroys $110B of infrastructure.

The two largest earthquakes of the past 40 years ruptured a 1600-kilometer-long portion of the fault boundary between the Indo-Australian and southeastern Eurasian plates on 26 December 2004 [seismic moment magnitude ( M w ) = 9.1 to 9.3] and 28 March 2005 ( M w = 8.6). The first event generated a tsunami that caused more than 283,000 deaths. Fault slip of up to 15 meters occurred near Banda Aceh, Sumatra, but to the north, along the Nicobar and Andaman Islands, rapid slip was much smaller. Tsunami and geodetic observations indicate that additional slow slip occurred in the north over a time scale of 50 minutes or longer.

This article simulates earthquake slip distributions as restricted random walks. Random walks offer several unifying insights into earthquake behaviors that physically based simulations do not. With properly tailored variables, random walks generate observed power law rates of earthquake number versus earthquake magnitude (the Gutenberg–Richter relation). Curiously, b -value, the slope of this distribution, not only fixes the ratio of small to large events but also dictates diverse earthquake scaling laws such as mean slip versus fault length and moment versus mean slip. Moreover, b -value determines the overall shape and roughness of earthquake ruptures. For example, mean random walk quakes with b = −½ have elliptical slip distributions characteristic of a uniform stress drop on a crack. Random walk earthquake simulators, tuned by comparison with field data, provide improved bases for statistical inference of earthquake behavior and hazard.

SUMMARY In the early morning of 1888 March 13, roughly 5 km 3 of Ritter Island Volcano fell violently into the sea northeast of New Guinea. This event, the largest lateral collapse of an island volcano to be recorded in historical time, flung devastating tsunami tens of metres high on to adjacent shores. Several hundred kilometres away, observers on New Guinea chronicled 3 min period waves up to 8 m high, that lasted for as long as 3 h. These accounts represent the best available first-hand information on tsunami generated by a major volcano lateral collapse. In this article, we simulate the Ritter Island landslide as constrained by a 1985 sonar survey of its debris field and compare predicted tsunami with historical observations. The best agreement occurs for landslides travelling at 40 m s −1 , but velocities up to 80 m s −1 cannot be excluded. The Ritter Island debris dropped little more than 800 m vertically and moved slowly compared with landslides that descend into deeper water. Basal friction block models predict that slides with shorter falls should attain lower peak velocities and that 40+ ms −1 is perfectly compatible with the geometry and runout extent of the Ritter Island landslide. The consensus between theory and observation for the Ritter Island waves increases our confidence in the existence of mega-tsunami produced by oceanic volcano collapses two to three orders of magnitude larger in scale.

SUMMARY NASA scientists have given a 1.1-km diameter asteroid (1950 DA) a 0.0 to 0.3 per cent probability of colliding with the Earth in the year 2880. This article examines a scenario where 1950 DA strikes the sea 600 km east of the United States coast. Travelling at 17.8 km s−1, the asteroid would blow a cavity 19 km in diameter and as deep as the ocean (5 km) at the impact site. Tsunami waves hundreds of metres high would follow as the transient impact cavity collapses. The tsunami disperses quickly; but because the waves are so large initially, destructive energy carries basin-wide. Within two hours of the scenario impact, 100-m waves make landfall from Cape Cod to Cape Hatteras. Within 12 hours, 20-m waves arrive in Europe and Africa. Water velocity at the deep ocean floor exceeds 1 m s−1 to 800-km distance, strong enough to leave a widespread tsunami signature in the sedimentary record.

The Exodus epic in the Hebrew Bible is associated with numerous environmental effects. When considered today from a twenty-first century perspective, many of these processes seem authentic. However, the Biblical narrative cannot be considered as scientific observation because there is an absence of concrete data concerning the chronology and location of many of the events that might be linked to environmental process hinted at in the ancient text. Nonetheless, the Exodus narrative has captured human imagination throughout the generations regardless of whether actual events inspired it. Since the late twentieth century, however, this epic attracted also an increasing number of researchers that have explored the possible influence of Bronze Age volcanic and earthquake activity in the eastern Mediterranean for their possible environmental effects that may be reflected in the Exodus narrative.

The preparation and characterization of three families of thermoplastic oligomers (Mn = 2918–13263 g mol−1) based on polyarylsulfone (PSU) differing in both molecular weight and terminal functionality and one series of polyarylethersulfone (PES) of different molecular weights is reported. Infrared and nuclear magnetic resonance spectroscopy data support the formation of both the hydroxyl terminated oligomers and conversion (67–89% depending on molecular weight) to the telechelic PSU oligomer bearing reactive benzoxazine groups. Differential scanning calorimetry reveals that the onset of homopolymerization in the telechelic PSU oligomer occurs at around 100°C (peak maximum 125°C at 10 K/min) and rescans show values of the glass transition (for the homopolymers) ranging from 124 to 167°C depending on molecular weight. The influence on the oligomer backbone and terminal functionality is examined using thermal analysis. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40875.

Geological evidence suggests that during a future eruption, Cumbre Vieja Volcano on the Island of La Palma may experience a catastrophic failure of its west flank, dropping 150 to 500 km³ of rock into the sea. Using a geologically reasonable estimate of landslide motion, we model tsunami waves produced by such a collapse. Waves generated by the run-out of a 500 km³ (150 km³) slide block at 100 m/s could transit the entire Atlantic Basin and arrive on the coasts of the Americas with 10–25 m (3–8 m) height.

We investigate the generation, propagation, and probabilistic hazard of tsunami spawned by oceanic asteroid impacts. The process first links the depth and diameter of parabolic impact cavities to asteroid density, radius, and impact velocity by means of elementary energy arguments and crater scaling rules. Then, linear tsunami theory illustrates how these transient cavities evolve into vertical sea surface waveforms at distant positions and times. By measuring maximum wave amplitude at many distances for a variety of impactor sizes, we derive simplified attenuation relations that account both for geometrical spreading and frequency dispersion of tsunami on uniform depth oceans. In general, the tsunami wavelengths contributing to the peak amplitude coincide closely with the diameter of the transient impact cavity. For the moderate size impactors of interest here (those smaller than a few hundred meters radius), cavity widths are less than or comparable to mid-ocean depths. As a consequence, dispersion increases the 1/□r long-wave decay rate to nearly 1/r for tsunami from these sources. In the final step, linear shoaling theory applied at the frequency associated with peak tsunami amplitude corrects for amplifications as the waves near land. By coupling this tsunami amplitude/distance information with the statistics of asteroid falls, the probabilistic hazard of impact tsunami is assessed in much the same way as probabilistic seismic hazard, by integrating contributions over all admissible impactor sizes and impact locations. In particular, tsunami hazard, expressed as the Poissonian probability of being inundated by waves from 2 to 50 m in height in a 1000-year interval, is computed at both generic (generalized geography) and specific (real geography) sites. For example, a typical generic site with 180° of ocean exposure and a reach of 6000 km, admits a 1-in-14 chance of an impact tsunami exceeding 2-m in height in 1000 years. The likelihood drops to 1-in-35 for a 5-m wave, and to 1-in-345 for a 25-m wave. Specific sites of Tokyo and New York have 1-in-24 and 1-in-47 chances, respectively, of suffering an impact tsunami greater than 5 m in the next millennium.

Earthquakes in California's San Francisco Bay Area are likely to be more strongly affected by stress interaction than earthquakes in any other place in the world because of the region's closely spaced, subparallel distribution of faults. I believe, therefore, that meaningful quantification of earthquake probability and hazard in the Bay Area can be made only with the guidance provided by physically based and regionwide earthquake models that account for this interaction. This article represents a first step in developing a standard physical earthquake model for the San Francisco Bay Area through realistic, 3000-year simulations of earthquakes on all of the area's major faults. These simulations demonstrate that a standard physical earthquake model is entirely feasible, they illustrate its application, and they blueprint its construction. A standard physical earthquake model provides the mechanism to integrate fully the diverse disciplines within the earthquake research community. As a platform for data utilization and verification, a physical earthquake model can employ directly any earthquake property that is measurable in the field or in the laboratory to tune and test its seismicity products. As a platform for probability forecasts, a physical earthquake model can supply rational estimates of every imaginable earthquake statistic while simultaneously satisfying all slip and earthquake rate constraints. As a platform for hazard analysis, a physical earthquake model can compute earthquake shaking intensity from first principles by convolving a full suite of rupture scenarios with site-specific dislocation Green's functions. Physical earthquake models have advanced greatly in the last decade. Simulations of earthquake generation and recurrence are now sufficiently credible that such calculations can begin to take substantial roles in scientific studies of earthquake probability and hazard. Manuscript received 9 March 1999.

In this paper, approximately 100 VLBI/SLR/GPS velocities map European strain rates from 9.0 × 10−8 yr−1 with regional uncertainties of 20 to 40 per cent. Kostrov’s formula translates these strain-rate values into regional geodetic moment rates M¯˙geodetic . Two other moment rates, M¯˙seismic , extracted from a 100-year historical catalogue and M¯˙plate , taken from plate-tectonic models, contrast the geodetic rates. In Mediterranean Europe, the ratios of M¯˙seismic to M¯˙geodetic are between 0.50 and 0.71. In Turkey the ratio falls to 0.22. Although aseismic deformation may contribute to the earthquake deficit (M¯˙seismic values less than M¯˙geodetic ), the evidence is not compelling because the magnitudes of the observed shortfalls coincide with the random variations expected in a 100-year catalogue. If the lack of aseismic deformation inferred from the 100-year catalogue holds true for longer periods, then much of Europe’s strain budget would have to be accommodated by more frequent or larger earthquakes than have been experienced this century to raise the ratios of M¯˙seismic to M¯˙geodetic to unity. Improved geological fault data bases, longer historical earthquake catalogues, and densification of the continent’s space geodetic network will clarify the roles of aseismic deformation versus statistical quiescence.

New and dense space geodetic data can now map strain rates over continental-wide areas with a useful degree of precision. Stable strain indicators open the door for space geodesy to join with geology and seismology in formulating improved estimates of global earthquake recurrence. In this paper, 174 GPS/VLBI velocities map United States’ strain rates of 30.0 × 10−8 yr−1 with regional uncertainties of 5 to 50 per cent. Kostrov’s formula translates these strain values into regional geodetic moment rates. Two other moment rates M¯˙seismic and M¯˙geologic , extracted from historical earthquake and geological fault catalogues, contrast the geodetic rate. Because M¯˙geologic , M¯˙seismic and M¯˙geodetic derive from different views of the earthquake engine, each illuminates different features. In California, the ratio of M¯˙geodetic to M¯˙geologic is 1.20. The near-unit ratio points to the completeness of the region’s geological fault data and to the reliability of geodetic measurements there. In the Basin and Range, northwest and central United States, both M¯˙geodetic and M¯˙seismic greatly exceed M¯˙geologic. Of possible causes, high incidences of understated and unrecognized faults probably drive the inconsistency. The ratio of M¯˙seismic to M¯˙geodetic is everywhere less than one. The ratio runs systematically from 70–80 per cent in the fastest straining regions to 2 per cent in the slowest. Although aseismic deformation may contribute to this shortfall, I argue that the existing seismic catalogues fail to reflect the long-term situation. Impelled by the systematic variation of seismic to geodetic moment rates and by the uniform strain drop observed in all earthquakes regardless of magnitude, I propose that the completeness of any seismic catalogue hinges on the product of observation duration and regional strain rate. Slowly straining regions require a proportionally longer period of observation. Characterized by this product, gamma distributions model statistical properties of catalogue completeness as proxied by the ratio of observed seismic moment to geodetic moment. I find that adequate levels of completeness should exist in median catalogues of 200 to 300 year duration in regions straining 10−7 yr−1 (comparable to southern California). Similar levels of completeness will take more than 20 000 years of earthquake data in regions straining 10−9 yr−1 (comparable to the southeastern United States). Predictions from this completeness statistic closely mimic the observed M¯˙seismic to M¯˙godetic ratios and allow quantitative responses to previously unanswerable questions such as: ‘What is the likelihood that the seismic moment extracted from an earthquake catalogue of X years falls within Y per cent of the true long-term rate?’ The combination of historical seismicity, fault geology and space geodesy offers a powerful tripartite attack on earthquake hazard. Few obstacles block similar analyses in any region of the world.

Geologists have been collecting, for decades, information from historical and paleoearthquakes that could contribute to the formulation of a “big picture” of the earthquake engine. Observations of large earthquake ruptures, unfortunately, are always going to be spotty in space and time, so the extent to which geological information succeeds in contributing to a grander view of earthquakes is going to be borne not only by the quantity and quality of data collected but also by the means by which it is interpreted. This article tries to understand geological data more fully through carefully tailored computer simulations of fault ruptures. Dogtails and rainbows are two types of fault rupture terminations that can be recognized in the field and can be interpreted through these models. Rainbows are concave down ruptures that indicate complete stress drop and characteristic slip. Rainbow terminations usually coincide with fault ends or strong segment boundaries. Dogtails are concave up ruptures that indicate incomplete stress drop and noncharacteristic slip. Dogtail terminations can happen anywhere along a fault or fault segment. The surface slip pattern of the magnitude 6.6, 1979 Imperial Valley, California, earthquake shows both dogtail and rainbow terminations. The rainbow confirms the presence of a strong fault segment boundary 6 km north of the international border that had been suggested by Sieh (1996). The dogtail implies that the displacement observed in 1979 is not characteristic. By combining paleoseismic information with the surface slip patterns from this event and the magnitude 7.1, 1940 Imperial Valley earthquake, I develop a quantitative Imperial fault model with northern, central, and southern segments possessing 50, 110, and 50 bar strength, respectively. Both the 1940 and 1979 events caused 1-m amplitude dogtailed ruptures of the northern segment; however, characteristic slip of the segment is more likely to be about 3 m. To illustrate the full spectrum of potential rupture modes, models were run forward in time to generate a 2000 year rupture “encyclopedia.” Even with well-constrained segmentation and strengths, modest changes in two friction law parameters produce several plausible histories. Further discrimination awaits analysis of the extensive paleoseismic record that geologists believe exists in the shore deposits of the intermittent lakes of the Salton Trough.

M max the maximum magnitude earthquake that a fault is likely to suffer, plays an important role in earthquake hazard estimation. Although observational evidence summarized in plots of characteristic earthquake magnitude (Mchar) versus fault length indicate that smaller faults produce lower magnitude events, an argument has been made that any fault regardless of its length should have Mmax near magnitude 8. The rationale for this argument charges that the contrary observational evidence stems from historical catalogs of limited extent and that it largely excludes nonconventional earthquakes in which several short and apparently disconnected fault segments fail simultaneously. This article addresses Mmax using computer models of rupture on faults of various strengths and configurations. Computer models have advantages in that (a) Mmax earthquakes always can be generated by forcing complete stress drop on fully stressed faults, thus avoiding the limitations of short historical catalogs, and (b) the circumstances necessary for the failure of several segments to contribute to a large Mmax can be investigated quantitatively. I find that for a strikeslip California environment, it is physically unlikely for an M 8 event to break less than 300 to 400 km of fault. Were this M 8 rupture to occur on as few as five independent segments, shear strength of the participating faults would have to be raised to implausible levels. If the fault segments are not independent and their coseismic stress fields interact, then amplifications in slip are possible without drastic increase in strength. The range of fault geometries where strong interactions and amplifications of stress occur, however, is very restricted, and discontinuous faults separated by even 5% of their length act more or less independently. Mmax earthquakes breading realistic-looking distributions of discontinuous faults rarely are more than 0.1-magnitude unit bigger than would be predicted from a moment summation based on the characteristic magnitude Mchar of each of the individual faults. A prudent course in hazard analysis differentiates Mmax from Mchar allowing Mmax to be 0.2 to 0.3 units larger than Mchar but not automatically equal to 8.

Morphologic characterisation of five distinct, eastern Australian upper continental slope submarine landslides enabled modelling of their tsunami hazard. Flow depth, run-up and inundation distance has been calculated for each of the five landslides. Future submarine landslides with similar characteristics to these could generate tsunami with maximum flow depths ranging 5–10 m at the coastline, maximum run-up of 5 m and maximum inundation distances of 1 km.

The absence of a long historical catalog of observed seismicity with which to constrain earthquake recurrence behaviors is a fundamental stumbling block to earthquake prediction in California. Conceding that this limitation is not likely to relax in the foreseeable future, alternative approaches must be sought to extend the catalog artificially. In this article, I evaluate the long-term behaviors of earthquakes on a map-like set of southern California faults through computer simulations that incorporate the physics of earthquake stress transfer and are constrained by excellent, but restricted, bodies of geological and seismological data. I find that model seismicity fluctuates on both short (decades) and long (centuries) timescales but that it possesses a well-defined mean and standard deviation. Seismicity fluctuations correlate across different magnitudes, and the long-term cycles of smaller events seem to lead cycles of larger events. Short-period seismicity fluctuations do not exhibit this tendency, and short-term changes in low-magnitude (M5 +) seismicity are not likely to be an effective predictor of future large events, at least for the region as a whole. As do real faults, the model faults produce characteristic and power law quakes in variable ratios with diverse periodic and nonperiodic behaviors. Generally, larger events tend to occur quasi-periodically, and smaller ones tend to cluster; however, only for a few earthquake classes and certain locations is recurrence notably non-Poissonian. An important use of synthetic seismicity is in the construction of earthquake hazard maps because it firmly grounds previously ad hoc assumptions regarding frequency-magnitude distributions, multiple-segment failure statistics, and rupture extents, while satisfying a spectrum of geological constraints such as fault slip rate, segment recurrence interval, and slip per event. With its depth of temporal and spatial coverage, synthetic seismicity also provides a means to investigate the time dependence of seismic hazard. Because hazard likelihood is a concatenation of the recurrence statistics from many seismic sources, in only about 40–50% of the regions near the major faults do sequences of 0.1 g or 0.2 g exceedances differ from Poissonian.

We find that the genesis of San Clemente Island and its surrounding submarine platform is consistent with progressive slip on two, southeast-striking, southwest-dipping, blind thrust fault segments. Since their inception 2 to 5 Ma, 3 km of compression normal to the N150°E fault strike has been accommodated with 1700 m of domal uplift of the San Clemente Anticlinorium. The existence of an extensive suite of Pleistocene marine terraces provides evidence that slip and uplift are continuing today. Based on direct terrace fossil age determinations and correlations of terrace heights with global sea-level curves, we estimate that San Clemente Island is currently uplifting at between 0.2 and 0.5 mm yr−1. This translates into 0.6–1.5 mm yr−1 of thrusting on the causative blind thrusts beneath the island. Unlike the situation at nearby Palos Verdes, where a simple twist in a regional strike-slip fault accommodated both fault-parallel and fault-normal motions, the shallow dips of the thrusts suggest that, if regional strike-slip motion on the San Clemente Fault exists, it must be partitioned onto through-going surfaces distinct from the thrusts. Current GPS data are sparse and equivocal, but they indicate that 1–4 mm yr−1 of compression and 4–7 mm yr−1 of strike slip are absorbed in the California Continental Borderland. With the Palos Verdes Fault taking some 3 mm yr−1 from the strike-slip budget, 1–4 mm yr−1 of motion could be present on a through-going San Clemente Fault. When translated into an annual moment release rate using Kostrov's formula, GPS strains predict that between 2.5 and 4.9 times 1017 N m yr−1 of earthquake potential is available offshore from San Diego to the Santa Barbara Channel. Distribution of this moment budget among various earthquake magnitudes is arguable, but we predict that M > 6 quakes in the Borderland could recur between 30 and 80 years, and M > 7 quakes might be found every 310 to 580 years.

This article develops several area-based tests of long-term seismic hazard predictions. The tests stem from the hypothesis that the observed fractional area of hazard exceedence should follow in proportion to the region's predicted likelihood of exceedence. For example, a prediction is successful if roughly 30% of the area mapped as having a 30% likelihood of exceeding some hazard threshold in a certain time interval, actually does suffer this level of shaking. Although tests of earthquake predictions are always equivocal, the success or failure of a forecast hazard map can be argued strongly from a statistical assessment of the hundreds of individual point predictions comprising the map. The specific forecasts to be examined are the 30-yr probabilities of peak ground acceleration exceedence that were presented by Ward (1994) for southern California. In lieu of a lengthy historical set of recorded peak accelerations, observational data for the tests were derived from the 150-yr earthquake catalog and standard attenuation relationships. In all cases, the observed hazard ratios were highly correlated with the predictions. Within 95% confidence bounds, the observed levels of hazard coincided with the predicted hazard from models that included a low-magnitude cutoff of M = 5.5 to 6, approximately the same limit as enlisted in the earthquake catalog. I propose a pass/fail criterion for acceleration hazard maps and I suggest that all seismic hazard predictions submit to area-based tests.