Geologic hazards such as earthquakes and landslides pose threats to communities in Kentucky. Landslides in particular cause millions of dollars in damage each year. Developing and implementing mitigation measures are the most effective ways to abate the impact of these hazards on communities. Earth scientists play important roles in the development and implementation of mitigation measures by providing the scientific basis—hazard maps in particular. It is critical that hazard maps be produced with the best science, but also that the meaning of the maps, as well as the associated uncertainties, be clearly and understandably communicated to the users and decision makers. The Kentucky Geological Survey (KGS) studies earthquakes and landslides and produces appropriate hazard maps that can be used by communities to develop mitigation measures. Furthermore, KGS works closely with communities and state agencies to help them understand and use the hazard maps.

The Mineral, Virginia (USA), earthquake occurred at 17:51:3.9 UTC (Coordinated Universal Time) on 23 August 2011; the hypocenter was at 37.905°N, 77.975°W and depth was 8 km. The widely reported moment magnitude (Mw) was 5.7 ± 0.1. The mb (teleseismic short-period) magnitude estimated here using 26 global network stations is 5.77 ± 0.23, in agreement with mb values reported by national and international data centers, and not significantly different from Mw. However, the mbLg magnitude of the earthquake determined here using 386 stations in eastern North America is 6.28 ± 0.26. The mbLg magnitude is a short-period magnitude correlated with mb that is based on the amplitude of the Lg phase at regional distances. Lg is a crust-guided phase that represents the largest amplitudes observed on short-period seismograms at regional distances in eastern North America. The mbLg magnitude was the primary magnitude appearing in catalogs of eastern United States earthquakes until superseded recently by Mw. The catalog of previous earthquakes in central Virginia is keyed to mbLg, rather than Mw. The Mineral shock reveals large regional variations in the Lg phase attenuation in the eastern United States. The expected value for the return period of mbLg 6.3 and larger earthquakes in the Central Virginia seismic zone is 752 yr, with a 95% confidence interval of 385–1471 yr. The Mineral earthquake caused Modified Mercalli Intensity (MMI) VIII damage in the epicentral area, with several instances of partial and total collapse of masonry chimneys and walls. A finite-fault, full wavefield simulation of the motions within 30 km of the epicenter fits the velocity recordings and Fourier spectral amplitudes in the 1–10 Hz frequency band, at the only strong-motion station in that distance range. The strongest motions are predicted to have occurred in two areas offset to the northwest and southeast of the epicenter, within which peak ground accelerations may have approached 2 g, and peak velocities were probably well in excess of 20 cm/s. The only factor mitigating damage in this earthquake was the brief (<3 s) duration of strong shaking.

We characterize shear-wave velocity versus depth (Vs profile) at 16 portable seismograph sites through the epicentral region of the 2011 Mw 5.8 Mineral (Virginia, USA) earthquake to investigate ground-motion site effects in the area. We used a multimethod acquisition and analysis approach, where active-source horizontal shear (SH) wave reflection and refraction as well as active-source multichannel analysis of surface waves (MASW) and passive-source refraction microtremor (ReMi) Rayleigh wave dispersion were interpreted separately. The time-averaged shear-wave velocity to a depth of 30 m (Vs30), interpreted bedrock depth, and site resonant frequency were estimated from the best-fit Vs profile of each method at each location for analysis. Using the median Vs30 value (270–715 m/s) as representative of a given site, we estimate that all 16 sites are National Earthquake Hazards Reduction Program (NEHRP) site class C or D. Based on a comparison of simplified mapped surface geology to median Vs30 at our sites, we do not see clear evidence for using surface geologic units as a proxy for Vs30 in the epicentral region, although this may primarily be because the units are similar in age (Paleozoic) and may have similar bulk seismic properties. We compare resonant frequencies calculated from ambient noise horizontal:vertical spectral ratios (HVSR) at available sites to predicted site frequencies (generally between 1.9 and 7.6 Hz) derived from the median bedrock depth and average Vs to bedrock. Robust linear regression of HVSR to both site frequency and Vs30 demonstrate moderate correlation to each, and thus both appear to be generally representative of site response in this region. Based on Kendall tau rank correlation testing, we find that Vs30 and the site frequency calculated from average Vs to median interpreted bedrock depth can both be considered reliable predictors of weak-motion site effects in the epicentral region.

Earthquake damage is often increased due to local ground-motion amplification caused by soft soils, thick basin sediments, topographic effects, and liquefaction. A critical factor contributing to the assessment of seismic hazard is detailed information on local site response. In order to address and quantify the site response at seismograph stations in the eastern United States, we investigate the regional spatial variation of horizontal:vertical spectral ratios (HVSR) using ambient noise recorded at permanent regional and national network stations as well as temporary seismic stations deployed in order to record aftershocks of the 2011 Mineral, Virginia, earthquake. We compare the HVSR peak frequency to surface measurements of the shear-wave seismic velocity to 30 m depth (Vs30) at 21 seismograph stations in the eastern United States and find that HVSR peak frequency increases with increasing Vs30. We use this relationship to estimate the National Earthquake Hazards Reduction Program soil class at 218 ANSS (Advanced National Seismic System), GSN (Global Seismographic Network), and RSN (Regional Seismograph Networks) locations in the eastern United States, and suggest that this seismic station–based HVSR proxy could potentially be used to calibrate other site response characterization methods commonly used to estimate shaking hazard.

A reconnaissance team documented the geotechnical and geological aspects in the epicentral region of the Mw (moment magnitude) 5.8 Mineral, Virginia (USA), earthquake of 23 August 2011. Tectonically and seismically induced ground deformations, evidence of liquefaction, rock slides, river bank slumps, ground subsidence, performance of earthen dams, damage to public infrastructure and lifelines, and other effects of the earthquake were documented. This moderate earthquake provided the rare opportunity to collect data to help assess current geoengineering practices in the region, as well as to assess seismic performance of the aging infrastructure in the region. Ground failures included two marginal liquefaction sites, a river bank slump, four minor rockfalls, and a ~4-m-wide, ~12-m-long, ~0.3-m-deep subsidence on a residential property. Damage to lifelines included subsidence of the approaches for a bridge and a water main break to a heavily corroded, 5-cm-diameter valve in Mineral, Virginia. Observed damage to dams, landfills, and public-use properties included a small, shallow slide in the temporary (“working”) clay cap of the county landfill, damage to two earthen dams (one in the epicentral region and one further away near Bedford, Virginia), and substantial structural damage to two public school buildings.

The 2011 Mineral, Virginia, earthquake is one of the larger recorded seismic events occurring east of the Rocky Mountains since seismic instrumentation was first deployed. The operation of the North Anna nuclear power station (NANPS), located ~22 km northeast of the epicenter, was affected by the earthquake vibration. This moderate event caused the first incident in which a commercial U.S. nuclear power plant experienced a safe shutdown as a result of earthquake ground motion. Post-earthquake investigations confirmed that important safety-related structures, systems, and components (SSCs) at the NANPS did not have any detectable damage. Damage at the NANPS consisted of cracking and spalling of some of the non-safety-related ancillary structures, and the plant was restarted after three months of intensive inspections and reviews. Response spectra developed from the recorded ground motion at the NANPS showed a modest exceedance of the plant seismic design levels for safety-related SSCs, but these SSCs were not damaged and maintained their functionality. The NANPS performance, in combination with other global examples, shows that nuclear power plants have been able to function safely even when earthquake ground motions exceeded the design levels of the SSCs. In this paper we describe the observed earthquake effects at the NANPS and discuss the original geologic and seismic characterization of the plant site. We also discuss the impacts of other earthquakes on the performance of various nuclear power plants, and previous and current seismic hazard and risk evaluations for U.S. nuclear power plants.

The moment magnitude (Mw) 5.8 Mineral, Virginia, earthquake of 23 August 2011, was centered ~130 km south-southwest of Washington, D.C. (USA), and caused minor damage across Virginia and the Washington metropolitan area. The Washington Monument sustained masonry damage; a post-earthquake survey of the monument performed for the National Park Service identified cracking and spalling of the pyramidion (the topmost piece of the obelisk), and cracking, spalling, and lesser damage over the entire length of the monument shaft. A seismic vulnerability assessment of the monument was then performed to evaluate the potential for damage to the monument from future earthquakes. No ground-motion recordings of the Mineral earthquake were available for the monument site; therefore, deterministic and probabilistic seismic hazard analyses were performed to develop site-specific response spectra representing the Mineral earthquake and the maximum considered earthquake (MCE). These spectra were initially developed for a firm rock site condition, and each event was represented by a suite of seven three-component time histories. The rock motions were then modified through site-response analyses to develop time histories and response spectra representing ground motions in the clayey and gravelly soils that support the base of the monument. The results of the site-response analysis show significant amplification at short to intermediate response periods; this amplification is also observed in recordings of the 2011 Mineral earthquake obtained from another site in the general vicinity of the monument. The ground shaking conditions, along with expected foundation load-deflection behavior, were used in detailed structural modeling of the monument to help understand the structure’s response and damage during the 2011 Mineral earthquake and to predict expected performance during future MCE-level ground shaking. The analyses indicate that the period range of the pyramidion’s modes of vibration corresponds closely with the characteristic period range of the monument’s subsurface profile, and is reflected by the peak response of the site-specific spectra analyzed for the Mineral scenario earthquake. This similarity caused amplification of motions experienced by the monument and increased damage to the pyramidion. The nonlinear analysis for the MCE ground motions indicates damage to the pyramidion similar to that from Mineral earthquake effects, but larger lateral displacements of the top of the shaft due largely to the greater soil-bearing stresses associated with a greater first-mode response. The monument was found to generally meet accepted seismic safety criteria without need for strengthening.

This paper investigates the potential causes of the damage to the Washington Monument sustained from the 2011 Mineral, Virginia (USA), earthquake through time-history dynamic analysis. Ambient vibration field test data were obtained and utilized to calibrate a finite element model of the structure and its foundation. The impact of the foundation modeling and the uncertainties associated with the material properties of the stone and iron, in the absence of in situ material testing, were investigated through several parametric studies, in which the material property values are permuted at three (upper, average, and lower) levels to bound the predicted dynamic characteristics of the structure. Because ground-motion data recorded in the Washington, D.C., area during the earthquake are scarce, the ground motion at the Washington Monument site was simulated using an angular transformation of the recorded ground motions in Reston, Virginia, deconvoluted to the bedrock level and upward propagation of the rotated motions to the ground surface based on soil profiles in Reston and the Washington Monument site provided by the U.S. Geological Survey. The finite element model of the Washington Monument shaft subjected to these bidirectional earthquake records showed high acceleration amplification at the observation level, as well as tensile stress concentration at the ~107 m level. These observations correlate with the damage observed in the pyramidion section and upper levels of the Washington Monument shaft following the 2011 Virginia earthquake.

The Mineral, Virginia (USA), earthquake of 23 August 2011 occurred at 6–8 km depth within the allochthonous terranes of the Appalachian Piedmont Province, rupturing an ~N36°E striking reverse fault dipping ~50° southeast. This study used the Interstate Highway 64 seismic reflection profile acquired ~6 km southwest of the hypocenter to examine the structural setting of the earthquake. The profile shows that the 2011 earthquake and its aftershocks are almost entirely within the early Paleozoic Chopawamsic volcanic arc terrane, which is bounded by listric thrust faults dipping 30°–40° southeast that sole out into an ~2-km-thick, strongly reflective zone at 7–12 km depth. Reflectors above and below the southward projection of the 2011 earthquake focal plane do not show evidence for large displacement, and the updip projection of the fault plane does not match either the location or trend of a previously mapped fault or lithologic boundary. The 2011 earthquake thus does not appear to be a simple reactivation of a known Paleozoic thrust fault or a major Mesozoic rift basin-boundary fault. The fault that ruptured appears to be a new fault, a fault with only minor displacement, or to not extend the ~3 km from the aftershock zone to the seismic profile. Although the Paleozoic structures appear to influence the general distribution of seismicity in the area, Central Virginia seismic zone earthquakes have yet to be tied directly to specific fault systems mapped at the surface or imaged on seismic profiles.

Occurring only 13 months apart, the moment magnitude, Mw 3.4 Germantown, Maryland (16 July 2010), and Mw 5.8 Mineral, Virginia (23 August 2011), earthquakes rocked the U.S. national capital region, drawing renewed attention to the occurrence of intraplate seismicity in the Mid-Atlantic region of the eastern United States. We model the Coulomb stress transferred by these earthquakes to fault zones in the Mid-Atlantic region that were active during the Cenozoic. In most cases, the Mineral earthquake brought these preexisting Cenozoic faults further from failure. This unloading, like all changes in stress located more than 30 km from the epicenter, was very small (~1–3 mbar) and therefore unlikely to affect the occurrence of earthquakes at the regional scale. Between 30 and 15 km away, however, the maximum Coulomb failure stress change ranged one to three orders of magnitude greater (~0.05–6 bar), levels on par with the stress changes that triggered historical earthquakes in California. The Mineral earthquake generated an increase in Coulomb failure stress of ~0.5 bar 10 km from the rupture, ~5 bar 5 km from the rupture, and ~20 bar at the edge of the rupture on receiver faults oriented like the mainshock. The geographic location of the aftershock-defined Northwest fault in the epicentral region may be explained by Coulomb stress transfer from the mainshock. Elastic dislocation modeling of surface deformation caused by the Mineral earthquake indicates a maximum of ~7 cm of permanent vertical surface displacement directly above the center of the rupture.

Observations made during geologic mapping prior to the moment magnitude, Mw 5.8 2011 Virginia (USA) earthquake are important for understanding the event. Because many Paleozoic ductile faults in the Piedmont of Virginia show signs of brittle overprint, relict faults in the epicentral area represent potential seismogenic surfaces in the modern stress regime. Three major faults that reportedly dissect the early-middle Paleozoic bedrock in the epicentral area are reviewed here: the Shores fault of uncertain age, which has been depicted as internal to the Early Ordovician or Cambrian metaclastic Potomac terrane; the Late Ordovician Chopawamsic fault, which represents the Potomac-Chopawamsic terrane boundary; and the late Paleozoic Long Branch fault, which is internal to the Middle Ordovician Chopawamsic terrane. Our mapping reveals no evidence for the Shores fault, as previously depicted, in the epicentral area, and has led to revision of the position and surface trace of the Chopawamsic fault. Both these features are considered to have no connection to the 2011 event. Ductile strain features in a previously unrecognized zone related to the Long Branch fault are considered with a simple analysis of aftershocks along the brittle Quail fault that followed the 2011 Virginia earthquake. Internal to the Chopawamsic Formation, this Bend of River high-strain zone coincides in three dimensions with the aftershock-defined fault plane for the 2011 event. The spatial coincidence of the modern seismogenic surface (Quail fault) and Paleozoic metamorphic fabrics leads us to interpret that this zone of Paleozoic ductile strain, now located in the shallow crust, served as a guide to modern brittle intraplate rupture in 2011.

The Stafford fault system, located in the mid-Atlantic coastal plain of the eastern United States, provides the most complete record of fault movement during the past ~120 m.y. across the Virginia, Washington, District of Columbia (D.C.), and Maryland region, including displacement of Pleistocene terrace gravels. The Stafford fault system is close to and aligned with the Piedmont Spotsylvania and Long Branch fault zones. The dominant southwest-northeast trend of strong shaking from the 23 August 2011, moment magnitude Mw 5.8 Mineral, Virginia, earthquake is consistent with the connectivity of these faults, as seismic energy appears to have traveled along the documented and proposed extensions of the Stafford fault system into the Washington, D.C., area. Some other faults documented in the nearby coastal plain are clearly rooted in crystalline basement faults, especially along terrane boundaries. These coastal plain faults are commonly assumed to have undergone relatively uniform movement through time, with average slip rates from 0.3 to 1.5 m/m.y. However, there were higher rates during the Paleocene–early Eocene and the Pliocene (4.4–27.4 m/m.y), suggesting that slip occurred primarily during large earthquakes. Further investigation of the Stafford fault system is needed to understand potential earthquake hazards for the Virginia, Maryland, and Washington, D.C., area. The combined Stafford fault system and aligned Piedmont faults are ~180 km long, so if the combined fault system ruptured in a single event, it would result in a significantly larger magnitude earthquake than the Mineral earthquake. Many structures most strongly affected during the Mineral earthquake are along or near the Stafford fault system and its proposed northeastward extension.

Mansurah, the eighth-century Arabic capital of Sindh province, Pakistan, flourished for a mere 200 yr. Its destruction by an earthquake ca. 980 A.D. was first proposed by archaeologists who reported the discovery of crushed skeletons amid dateable coins found among its rubble. An abrupt natural death to the city was challenged by others who noted that the absence of wood or valuables was consistent with the city being sacked and systematically looted. The recent discovery of four decorated door knockers beneath the collapsed walls of one of the largest structures in Mansurah, however, reopens the case for an earthquake, since an invading army would almost certainly have removed them as booty. We suggest that an earthquake not only destroyed the city and its suburbs (intensity ≈ VIII), but resulted in postseismic avulsion of the river on which its citizens depended for agriculture, sanitation, and trade. Since natural levees have been observed in India to collapse in intensity VII shaking, it is unnecessary to invoke coseismic uplift as a requirement for upstream river avulsion. The absence in the past two centuries of large earthquakes in the region has resulted in central Sindh being depicted as a region of low seismic hazard, yet in 1668, in the same province, an earthquake destroyed nearby Samawani and also initiated avulsion of the Indus. A case can be made for reevaluating the five millennia of archaeological ruins in Pakistan to establish a long-term view of seismicity unavailable from the short instrumental record.

Srinagar, the capital city of Kashmir, has been shaken numerous times by earthquakes in the past millennium, most recently by damaging earthquakes in 1885 (M 6.2, 30 km to the west) and 2005 (M 7.6, 200 km to the west) with estimated EMS (European Macroseismic Scale) intensity VI–VII. Earthquakes in Kashmir in earlier historical times are known only from fragmentary archival sources. We present and analyze unique, repeat photographs of the Pandrethan Temple near Srinagar, which we conclude can provide clues to the severity of nineteenth-century earthquakes. Photos taken in 1868 and 1885 and recently show that the temple, a 5.5-m-square masonry-block structure constructed ca. A.D. 920, was undamaged by these two earthquakes. We conclude that displaced blocks visible in the earliest extant photograph are the result of stronger shaking in the past, the most probable causal earthquake being in 1828. Considering the fragility of the structure, we conclude that anything greater than EMS intensity IX would have caused structural collapse. We thus conclude that Pandrethan has not experienced EMS intensity greater than VIII in the past 200 yr, and possibly not in the past millennium.

The ruins of the ancient settlement of “El Tolmo de Minateda” are one of the best representative archaeological sites within the Albacete Province (SE Spain), characterized by a well-preserved record for the last ~3800 yr. The present ruins record an almost continuous of occupation from the Late Bronze Age (Iberian Culture, from ca. third century B.C.) to the High Middle Ages, including intervening and successive Roman, Visigoth, and Muslim city remains. The eventual Muslim settlement was abruptly abandoned and destroyed during the ninth–tenth centuries A.D., leaving a lack of any archaeological evidence of war or decay. Another previous anomalous archaeological episode of abrupt city abandonment and destruction is recorded during the Visigothic Period (seventh century). The archaeological record of this city supports evidence for earthquake damage linked to both periods of city abandonment and destruction, including oriented collapse of walls, watchtowers, and columns, oriented cracking of walls and column drums, as well as in situ broken pottery, abrupt abandonment of kilns, and anomalous sedimentary infilling of canals and water-supply facilities. Additionally, large-scale rockfalls containing Visigothic carved tombs are also apparently associated with both episodes, constituting one of the few instances of combined geoarchaeological evidence of earthquake ground effects ever reported. As a means of testing the theoretical archaeoseismic potential of this site, we obtained an archaeoseismic quality factor (AQF) value of 0.074.

The field trip guide describes nine stops that examine the mechanisms and timing of some of the abundant and often gigantic landslides that occur along the Winter Ridge–Slide Mountain escarpment in south-central Oregon. Subsidence of Summer Lake basin, situated in the northwestern Basin and Range province, has exposed a kilometer-thick Neogene sequence of dense volcanic flow rocks overlying very weak tuffaceous sedimentary rocks in the bounding escarpment. Subsidence is accommodated on the 58-km-long Winter Rim fault system, a normal fault which is capable of producing Mw ≈ 7 earthquakes with near-field, maximum horizontal acceleration approaching 1 g on the bedrock footwall. Gigantic rock slides cubic kilometers in volume scallop the southwestern portion of the escarpment, and their deposits run out as rock avalanches several kilometers onto the basin floor. Limit-equilibrium slope stability analyses support observations that these gigantic bedrock landslides initiate within the weak tuffaceous sedimentary rocks along shallow, east-dipping, planar failure surfaces one to two kilometers in length; are insensitive to groundwater fluctuations; and, are stable under static conditions. Strong ground motions appear requisite to trigger landsliding and are necessary to replicate the long, shallow failure surfaces. Landslide, colluvial, and lacustrine deposits on the hanging wall have undergone widespread post-emplacement deformation, which may involve large-scale seismogenic lateral spreading and flow sliding controlled by the saturated, fine-grained basin fill.

Performance of a high-level nuclear waste repository at Yucca Mountain hinges partly on long-term structural stability of the mountain, its susceptibility to tectonic disruption that includes fault displacement, seismic ground motion, and igneous intrusion. Because of the uncertainty involved with long-term (10,000 yr minimum) prediction of tectonic events (e.g., earthquakes) and the incomplete understanding of the history of strain and its mechanisms in the Yucca Mountain region, a tectonic model is needed. A tectonic model should represent the structural assemblage of the mountain in its tectonic setting and account for that assemblage through a history of deformation in which all of the observed deformation features are linked in time and space. Four major types of tectonic models have been proposed for Yucca Mountain: a caldera model; simple shear (detachment fault) models; pure shear (planar fault) models; and lateral shear models. Most of the models seek to explain local features in the context of well-accepted regional deformation mechanisms. Evaluation of the models in light of site characterization shows that none of them completely accounts for all the known tectonic features of Yucca Mountain or is fully compatible with the deformation history. The Yucca Mountain project does not endorse a preferred tectonic model. However, most experts involved in the probabilistic volcanic hazards analysis and the probabilistic seismic hazards analysis preferred a planar fault type model.

Attempts to study earthquake recurrence in space and time are limited by the short history of instrumental seismology compared to the long and variable recurrence time of large earthquakes. As a result, apparent concentrations and gaps in seismicity and hence seismic hazard within a seismic zone, especially where deformation rates are slow (<10 mm/yr), are likely to simply reflect the short earthquake record. Simple numerical simulations indicate that if seismicity were uniform within a tectonically similar seismic zone, such as the Atlantic coast of Canada, St. Lawrence valley, or the coast of North Africa, thousands of years of record would be needed before apparent concentrations and gaps of seismicity and hazard did not arise. Hence, treating sites of recent seismicity as more hazardous for future large earthquakes is likely to be inappropriate, and it would be preferable to regard the hazard as comparable throughout the seismic zone.

We present data and models for the present-day stress and strain pattern in the Pannonian Basin and surrounding East Alpine–Dinaric orogens. Formation of the Pannonian Basin within the Alpine mountain belt started in the early Miocene, whereas its compressional reactivation has been taking place since late Pliocene–Quaternary time. Basin inversion is related to changes in the stress field from a state of tension during basin formation in the Miocene to a state of compression resulting from the convergence between the Adria microplate and the European plate. Seismicity indicates that deformation is mainly concentrated along Adria's boundaries where pure contraction (thrusting in Friuli and the southeastern Dinarides), often in combination with transform faulting (dextral transpression in the central Dinarides), is predominant. Tectonic stresses and deformation are transferred into the Pannonian Basin, resulting in a complex pattern of ongoing tectonic activity. From the margin of Adria toward the interior of the Pannonian Basin, the dominant style of deformation gradually changes from pure contraction, through transpression, to strike-slip faulting. Shortening in the basin system, documented by earthquake focal mechanisms, global positioning system (GPS) data, and the neotectonic habitat, has led to considerable seismotectonic activity and folding of the lithosphere. The state of recent stress and deformation in the Pannonian Basin is governed by the interaction of plate-boundary and intraplate forces, which include the counterclockwise rotation and N-NE–directed indentation of the Adria microplate (“Adria-push”) as the dominant source of compression, in combination with buoyancy forces associated with differential topography and lithospheric heterogeneities.

The tectonic setting of Australia has much in common with North America east of the Rocky Mountains because stable continental crust makes up the whole continent. The seismicity is still sufficient to have caused several damaging earthquakes in the past 50 yr. However, uncertainties in the earthquake catalogue limit the reliability of hazard models. To complement traditional hazard estimation methods, alternative methods such as paleoseismic, geodynamic numerical models and high-resolution global positioning system (GPS) are being investigated. Smoothed seismicity analysis shows that seismic recurrence varies widely across Australia. Despite the limitations of the catalogue, comparisons of regional strain rates calculated from the seismicity are consistent with data derived from geodetic techniques. Recent paleoseismic studies, particularly those examining high-resolution digital elevation models, have identified many potential prehistoric fault scarps. Detailed investigation of a few of these scarps suggests that the locus of strain release is migratory on a time scale an order of magnitude greater than the instrumental seismic catalogue, consistent with Aus tralia's low-relief landscape. Numerical models based on the properties of the Australian plate provide alternative constraints on long-term crustal deformation. Two attenuation models for Australia have recently been developed. Because Australia is an old, deeply weathered continent that has experienced little Holocene glaciation, it has very little material comparable to North American “hard rock” site classification. The combination of relatively low attenuation crust under widespread thick weathered regolith makes the use of ground-motion and site response models derived from Australian data vital for Australian hazard assessment. Risk modeling has been used to assess sensitivities associated with variations in both source and ground-motion models. Systematic analyses allow the uncertainty in these models to be quantified. Uncertainty in most input models contributes a 30%–50% variation in the predicted loss. Where a city lies in a thick sedimentary basin, such as Perth, uncertainties in the behavior of the basin can result in a 500% variation in predicted loss.