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The Mediterranean region is increasingly experiencing intense and short-term rainfall, whose effects on the ground trigger widespread and quickly evolving phenomena including debris flows and shallow landslides which cause damage to buildings and infrastructure and occasionally even loss of life. In this research, we focus on the central Mediterranean in an area exposed to high-intensity rainfall that impacts small catchments which have been intensively anthropogenically modified through the years. The Portofino Promontory is characterized by a high cultural and landscape value where nature and historical anthropogenic landforms and signs coexist. The Promontory attracts tourists from all over the world, but it is exposed to a high number of hazards related to debris–mud flow processes that may impact cultural heritage, tourism facilities and infrastructure. In addition, the ancient man-made terraces that are widespread along the Promontory’s slopes may play the role of being a source for shallow landslides, as this similarly happens in many Mediterranean regions. In 2011, heavy rainfall impacted the similar landscape of the Cinque Terre, triggering hundreds of small mud–debris flows whose combined effect was devastating. To this end, a ground effects simulation was developed as part of the H2020 project RECONECT which aims to contribute to a European reference framework on nature-based solutions, based on the high-detail and -precision remote sensing data acquired within the project. The data allowed us to assess the triggering areas, the transport channel, the observed deposition zones and the interaction with the exposed elements before building a possible risk scenario. The simulation and the entire approach may be upscaled to many similar areas where shallow landslide hazards originating from man-made terraces threatens buildings, cultural heritage, tourism facilities and infrastructure.

[This corrects the article DOI: 10.1371/journal.pone.0243619.].

Unique geological and seismotectonic settings may trigger a multicascading hazard and should be identified beforehand. Such is the head of the Gulf of Elat–Aqaba (HGEA) at the northeastern end of the Red Sea where its geology, tectonics, bathymetry, and earthquake and tsunami history exhibit clear potential for earthquake and submarine-landslide tsunami generation. We thus investigated the possible tsunamigenic sources in the gulf and evaluated the resulting hazard at the HGEA. First, we assembled a bathymetric grid and adopted GeoClaw software to simulate most of the earthquake-tsunami scenarios. Next, we resolved the scheme of the largest possible tsunamigenic earthquakes along the deep basins of the Gulf of Elat (GEA) and the associated Dead Sea rift valley, as well as the potential tsunamigenic submarine landslides in the HGEA. The use of GeoClaw was verified against the 1995 tsunami generated by the Nuweiba Mw 7.2 earthquake, and then operated to simulate a suite of earthquake scenarios. Results showed that the marginal faults of Elat Basin pose the highest tsunami hazard to the Israeli part of the HGEA. To better assess that hazard, we screened the geology and seismotectonics of the HGEA and found that the Elat normal fault presents the worst-case scenario for Elat city. It is capable of generating a multicascading threat of earthquake and submarine-landslide tsunami, local subsidence that can increase inundation, and above all, destructive ground motion. Scenarios of a tsunami caused by the worst-case earthquake on the Elat fault simulated by GeoClaw and Ward’s (Tsunami, The encyclopedia of solid earth geophysics. 2011, 1473–1493) approach, and submarine landslide in the HGEA simulated by Wang et al.’s (Geophys. J. Int., 2015, 201, 1534–1544) ‘Tsunami Squares’ approach, demonstrated waves as high as 4 m along these coasts. Accordingly, we constructed a map of the evacuation zone. We also show that strong ground-shaking and retreat of the sea at the HGEA should be considered a tsunami warning, although false alarms are inevitable. Furthermore, tsunami hazard exists all along the gulf and further assessments are needed to quantify this hazard and increase awareness among the area's population.

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.

Most analyses of storm surge and inundation solve equations of continuity and momentum on fixed finite-difference/finite-element meshes. I develop a completely 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. In addition to being more intuitive than traditional methods, the tsunami ball approach has several advantages. (a) By tracking water balls of fixed volume, the continuity equation is satisfied automatically and the advection term in the momentum equation becomes unnecessary. (b) The procedure is meshless in the finite-difference/finite-element sense. (c) Tsunami balls care little if they find themselves in the ocean or inundating land. (d) Tsunami ball calculations of storm surge can be done on a laptop computer. I demonstrate and calibrate the method by simulating storm surge and inundation around New Orleans, Louisiana caused by Hurricane Katrina in 2005 and by comparing model predictions with field observations. To illustrate the flexibility of the tsunami ball technique, I run two “What If” hurricane scenarios—Katrina over Savannah, Georgia and Katrina over Cape Cod, Massachusetts.

The Mediterranean region is increasingly experiencing intense and short-term rainfall, whose effects on the ground trigger widespread and quickly evolving phenomena including debris flows and shallow landslides which cause damage to buildings and infrastructure and occasionally even loss of life. In this research, we focus on the central Mediterranean in an area exposed to high-intensity rainfall that impacts small catchments which have been intensively anthropogenically modified through the years. The Portofino Promontory is characterized by a high cultural and landscape value where nature and historical anthropogenic landforms and signs coexist. The Promontory attracts tourists from all over the world, but it is exposed to a high number of hazards related to debris–mud flow processes that may impact cultural heritage, tourism facilities and infrastructure. In addition, the ancient man-made terraces that are widespread along the Promontory's slopes may play the role of being a source for shallow landslides, as this similarly happens in many Mediterranean regions. In 2011, heavy rainfall impacted the similar landscape of the Cinque Terre, triggering hundreds of small mud–debris flows whose combined effect was devastating. To this end, a ground effects simulation was developed as part of the H2020 project RECONECT which aims to contribute to a European reference framework on nature-based solutions, based on the high-detail and -precision remote sensing data acquired within the project. The data allowed us to assess the triggering areas, the transport channel, the observed deposition zones and the interaction with the exposed elements before building a possible risk scenario. The simulation and the entire approach may be upscaled to many similar areas where shallow landslide hazards originating from man-made terraces threatens buildings, cultural heritage, tourism facilities and infrastructure. [ABSTRACT FROM AUTHOR]

Landslide is a frequent geological hazard in the Three Gorges reservoir area of China. Impulse waves could be created and cause substantial damage if the landslide collides with a water body. A nonlinear shallow water equation in combination with a progressive landslide model is proposed to simulate this catastrophic disaster. The proposed approach is distinguished by rapid calculation, less computational burden, and high practical value. By simulating the 2008 Three Gorges Reservoir Gongjiafang landslide and the subsequent impulse waves, we illustrated and validated this methodology. The initiation and motion processes of the landslide, as well as the generation, propagation, and run-up processes of impulse waves, were thoroughly performed. The simulation results were in good agreement with the field survey data, demonstrating the viability of the proposed approach for simulating the impulse waves triggered by landslide events. This numerical approach is beneficial for engineers to perform a preliminary estimation of landslide-generated waves and further facilitate the prevention and mitigation of geological hazards. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The Red Sea is a maritime rift. Tsunamigenic submarine landslides are common in these deep, steep‐sided, and seismically active basins. Because the rift is narrow, tsunami formed on one margin dissipate little before impacting the opposite side. Red Sea slope failures are therefore especially hazardous. We examine the tsunamigenic potential of an incipient landslide in the Tiran Straits that started, but then stopped after a short distance. Radiometric and biotic analyses fix the age of this landslide to within the last 500 years. Tsunami modeling of the incipient slide predicts ∼10 m wave heights on the Egyptian coastline. Of present concern is that the slope will eventually slide to completion with even more hazardous results. Tsunami simulated for this future event are twice as large as that generated by the incipient slide, so the threat posed by a future slide is consequential. Sharm El Sheikh, an Egyptian resort town now lies in its path, as does "The Line," a vast Saudi infrastructure project. This study warns of credible tsunami risk in the rapidly urbanizing Tiran Straits. Plain Language Summary: We present the discovery of an incipient submarine landslide in the Tiran Straits. Our study reveals how even incipient submarine landslides can spawn tsunami as tall as those from Mw = 9 earthquakes, at least locally. Incipient failures also carry the dual threat of eventually sliding to completion, yielding still larger tsunami sometime in the future. Should this incipient slide complete, it will gravely threaten the rapidly urbanizing coastline of the Tiran Straits and adjacent Gulf of Aqaba. Key Points: An incipient submarine landslide started in the Tiran Straits, stalled, but likely still generated a 10 m tsunamiTsunami produced by slides are fundamentally different from those formed by earthquake ruptures ‐ even incipient landslides can spawn tsunami as tall as those from Mw = 9 earthquakes, at least locallyIncipient failures also carry the dual threat of eventually sliding to completion, yielding still larger tsunami sometime in the future. This hazard is especially amplified in narrow basins like the Red Sea [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

On 4 April 2013, a 1.5 million cubic meter landslide occurred in Sunjia Town, Wanzhou County, Three Gorges Reservoir, China. After initiation, the Sunjia landslide traveled about 30 m toward the northeast and destroyed most of the infrastructure in its path. The landslide was triggered by heavy rainfall and previous slope excavations, but this slope also displayed a complicated failure process: the overlying earth slope first deformed and then induced sliding along underlying rock surfaces. Surface displacements that resulted from continuous creeping of the post-event slope were observed by an emergency monitoring system that revealed the disequilibrium state of the slope. To discuss the stability and future movements of the remaining unstable debris deposits, we developed a geotechnical model of the post-slide slope, calculated how it can slide again in an extreme rainfall scenario, and estimated the potential runout distance using the Tsunami Squares method. We then estimated the number of people and the value of the infrastructure threatened by this potential landslide. Lastly, we analyzed the vulnerability of elements at risk and quantitatively evaluated the hazard risk associated with the most dangerous scenario. This quantitative risk analysis provides a better understanding of, and technical routes for, hazard mitigation of rainfall-induced complex landslides. [ABSTRACT FROM AUTHOR]

A rainfall-induced complex landslide occurred on April 4, 2013, in Wanzhou County, Three Gorges Reservoir, China. Approximately 1.5 × 106 m3 of earth and rock mass slid over a distance of ~ 30 m, destroying residential buildings and rural roads. We perform a comprehensive assessment of the cause of this landslide using field surveys, borehole drillings, and interpretations of aerial photographs. This landslide exhibited a complex failure mode in which the upper part of the earth slope first deformed and slid along geotechnical interfaces. This then triggered the slide of the lower part of the flysch bedding rock. In this study, the landslide mass was divided into nine separate blocks considering their internal geological features and movements. The study also shows that antecedent rainfall, in association with the geological and morphological features of the steep slope, the presence of weak interlayers, and human interventions such as slope excavations, jointly caused this disaster. This well-observed event study facilitates comprehensive recognition of the deformation characteristics and failure mechanisms of rainfall-induced complex landslides and also provides an insight into landslide hazard mitigation. [ABSTRACT FROM AUTHOR]

On 2015 June 24, a 230 000 m3 landslide slid into the triangle bayou at the intersection of the Yangtze and Daning Rivers and generated a river tsunami that ran up 6.2 m on the opposite shoreline at Wushan town. The slope failure and resulting waves killed two people and damaged many shipping facilities. Based on field surveys and eyewitness observations, we apply the 'Tsunami Squares' method to model the Hongyanzi landslide and its generated waves. Landslide simulations indicate a maximum impact velocity of ∼16 m s−1 that matches well with an eyewitness video. The computed post-slide mass stopped on the near river bed with a shape fitting the observed geological profile. Tsunami simulations reveal a large region of wave impacts that coincide with the observed run-up heights. The successful reproduction of the dynamics of this landslide-generated river tsunami emphasizes the capacity and efficiency of Tsunami Squares modelling in emergency reaction and risk assessment. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The article lists the editors who are working for periodical "Landslides" as of 2015 including Alexander Strom from Geodynamic Research Center, Clemente Irigaray from University of Granada, Spain and Davide Notti from Universidad de Granada.

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. [ABSTRACT FROM AUTHOR]

How are individuals affected when the communities they live in change for the worse? This question is central to understanding neighborhood effects, but few study designs generate estimates that can be interpreted causally. We address issues of inference through a natural experiment, examining post-traumatic stress at multiple time points in a population differentially exposed to the 2004 Indian Ocean tsunami. The data, from the Study of the Tsunami Aftermath and Recovery, include interviews with over 16,000 Indonesian adults before and after the event. These data are combined with satellite imagery, direct observation, and informant interviews to examine the consequences of community destruction for post-traumatic stress. Using multilevel linear mixed models, we show that community destruction worsens post-traumatic stress, net of rigorous controls for individual experiences of trauma and loss. Furthermore, the effect of community destruction persists over time and extends across a wide range of community types. [ABSTRACT FROM AUTHOR]

The 12 September 2007 great Bengkulu earthquake ( M 8.4) occurred on the west coast of Sumatra about 130 km SW of Bengkulu. The earthquake was followed by two strong aftershocks of M 7.9 and 7.0. We estimate coseismic offsets due to the mainshock, derived from near-field Global Positioning System (GPS) measurements from nine continuous SuGAr sites operated by the California Institute of Technology (Caltech) group. Using a forward modelling approach, we estimated slip distribution on the causative rupture of the 2007 Bengkulu earthquake and found two patches of large slip, one located north of the mainshock epicenter and the other, under the Pagai Islands. Both patches of large slip on the rupture occurred under the island belt and shallow water. Thus, despite its great magnitude, this earthquake did not generate a major tsunami. Further, we suggest that the occurrence of great earthquakes in the subduction zone on either side of the Siberut Island region, might have led to the increase in static stress in the region, where the last great earthquake occurred in 1797 and where there is evidence of strain accumulation. [ABSTRACT FROM AUTHOR]

Most analyses of storm surge and inundation solve equations of continuity and momentum on fixed finite-difference/finiteelement meshes. I develop a completely 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. In addition to being more intuitive than traditional methods, the tsunami ball approach has several advantages. (a) By tracking water balls of fixed volume, the continuity equation is satisfied automatically and the advection term in the momentum equation becomes unnecessary. (b) The procedure is meshless in the finite-difference/finite-element sense. (c) Tsunami balls care little if they find themselves in the ocean or inundating land. (d) Tsunami ball calculations of storm surge can be done on a laptop computer. I demonstrate and calibrate the method by simulating storm surge and inundation around New Orleans, Louisiana caused by Hurricane Katrina in 2005 and by comparing model predictions with field observations. To illustrate the flexibility of the tsunami ball technique, I run two "What If " hurricane scenarios-Katrina over Savannah, Georgia and Katrina over Cape Cod, Massachusetts. [ABSTRACT FROM AUTHOR]

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-to-particle 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. [ABSTRACT FROM AUTHOR]

We estimate the critical slip-weakening distance on in-slab earthquake faults in a subduction zone, by applying a recent approach proposed by us. This approach is to find a relation between the breakdown time of shear stress , the time of peak slip velocity , and the slip-weakening distance from the time histories of shear stress, slip and slip velocity at each point on the fault. The previous results show that at can be well approximated by at for faults even with a heterogeneous stress drop distribution, except at locations near barriers and fault edges. We apply the above method to three large in-slab, normal-faulting earthquakes in the Mexican subduction zone. To do this, we calculate the spatial distribution of slip-velocity functions and final slip from kinematic waveform inversion of strong-motion and teleseismic records, and the stress history and final stress change from dynamic rupture calculations. By integrating the slip-velocity functions obtained from the inversion, from the rupture arrival time to the time of peak slip velocity, we obtain slip at and then correct it for at through dynamic calculations. We also estimate the lowest resolvable limit and probable errors of from the slip-velocity functions, and its upper bound from a theoretical constraint between the dynamic stress drop and . We found that the slip-weakening distance estimated in the frequency band between 0.05 and 0.5 Hz ranges between 40 and 120 cm on the in-slab fault of the 1999 Oaxaca earthquake . The largest is detected in the central fault and in part of the deeper sections, and in the zone around the hypocentre ranges between 50 and 70 cm. The estimated values appear to be less depth-dependent but are rather more dependent on the local maximum slip. This possible slip dependence might be interpreted by the degree of fault roughness, in addition to stress heterogeneities. The fracture energy G in the central section and in the hypocentral zone are roughly estimated to be of the order of 10–15 and 5–8 MJ m−2, respectively. Both of the estimated and G values are somewhat larger than those on the vertical fault of two recent, shallow strike-slip earthquakes in western Japan. [ABSTRACT FROM AUTHOR]

Focuses on the tsunamic and lateral collapse of the Ritter Island volcano in New Guinea in 1988. Observations and inferences concerning the tsunami, the collapse and the landslide deposits; Consensus between theory and observation for the Ritter Island waves.

Examines a scenario where the asteroid 1950 DA strikes the sea 600 km east of the U.S. coast. Diameter and depth of the cavity that would appear at the impact site; Generation of tsunami waves; Water velocity at the deep ocean floor.

Examines the potential environmental hazards of volcanoes located around the Pacific Ocean. Computer simulation of tsunami waves; Low-dust impact; Mass extinction.

Examines the of measurement of the earthquake and space strain rates in Europe. Deformation of the seismic arrays; Consistency of the dense space geodetic data; Rotation of the plate-tectonic models.

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 <0.03 to >30.0 × 10[sup -8] yr[sup -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 ...[sub seismic] and ...[sub geologic], extracted from historical earthquake and geological fault catalogues, contrast the geodetic rate. Because ... geologic, ...[sub seismic] and M[sub geodetic] derive from different views of the earthquake engine, each illuminates different features. In California, the ratio of ...[sub geodetic] to ...[sub 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 ...[sub geodetic] and ...[sub seismic] greatly exceed ...[sub geologic]. Of possible causes, high incidences of understated and unrecognized faults probably drive the inconsistency. The ratio of ...[sub seismsic] to ...[sub 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... [ABSTRACT FROM AUTHOR]

Surface deformation and a tsunami accompanied the destructive April 22, 1991, Costa Rica-Panamá earthquake (Ms = 7.5). Along a 135 km stretch of Caribbean coast, coseismic uplift was measured between the lower and upper limits of sessile intertidal organisms stranded on coral reefs, the preearthquake and postearthquake high tide levels located from driftwood lines on beaches, and the preearthquake and postearthquake tide levels as pointed out by local residents. The nature and distribution of offshore vertical displacements were further constrained from analysis of measured run-up heights and reported arrival times of the tsunami. Uplift detected along the coast jumped, within 4 km, from zero to 157 cm near Limón and generally decreased over a distance of 70 km southward to the border with Panamá. These data map an axis of uplift that intersects the coastal beach ridge just north of the port of Moín and runs offshore to the east and south roughly parallel to the coast. No surface faulting was found. The earthquake and tsunami were generated by backarc thrusting along faults that bound the north Panamá deformed belt and dip from the Caribbean Sea beneath Costa Rica and northern Panamá. Combined geodetic and seismological data indicate that the main rupture dips landward at an angle of about 30° and is approximately 40 km wide and 80 km long. Dislocation models suggest 2.2 m of slip on a causative thrust fault striking between 105° and 120°. We estimate that the repeat time for this type of earthquake is 200 to 1100 years. The historical record and new isotopic data favor the middle of the range. [ABSTRACT FROM AUTHOR]