Search

The duration of strong shaking is particularly important for assessing building performance, potential landslides and liquefaction hazards. The results of this investigation can potentially help reduce related fatalities and economic losses. In this study, we analyzed the acceleration seismograms of the Taiwan strong motion network to characterize the strong shaking duration associated with earthquake sources, propagation paths and site effects. This study proposes a new definition for the strong shaking duration called “effective shaking duration” (ESD), which considers the amplitude and radiation energy decays. We first consider the window of a time series during which the amplitude is ≥0.01 g, and we then defined the ESD as the length of the interval of the dissipated energy within 5–95 % of the total energy during this time frame. We calculated the strong shaking duration for 495 inter-plate events with magnitudes of M L > 5.0 and focal depths

Debris flows frequently occurred in Wenchuan earthquake region from 2008 to 2010, resulting in great damage to localities and being a prolonged threat to reconstruction. Forty three events' data including debris-flow volume, sediment volume and watershed area are analyzed and compared with other debris-flow events in Eastern Italian Alps, burned areas in USA and in Taiwan. The analysis reveals that there is a strong empirical relationship between debris-flow volume and loose materials volume in the earthquake region. In addition, the relationship between debris-flow volume and watershed area in the earthquake region has a wider variation range than that in other three regions while the debris volume also appears to be larger than that in the other three regions, which implies the volume of debris flows with strong influence of earthquakes is larger than that with no such influence and it is hard to predict the post-quake volume only by the watershed area. The comparison of the maximal debris-flow erosion modulus in the Wenchuan region and in Taiwan indicates that debris flows will be very active in a short time after strong earthquake.

A general approach for the estimation of tsunami height and hazard in the vicinity of active volcanoes has been developed. An empirical relationship has been developed to estimate the height of the tsunami generated for an eruption of a given size. This relationship can be used to estimate the tsunami hazard based on the frequency of eruptive activity of a particular volcano. This technique is then applied to the estimation of tsunami hazard from the eruption of the Augustine volcano in Alaska. Modification of this approach to account for a less than satisfactory data base and differing volcanic characteristics is also discussed with the case of the Augustine volcano as an example. This approach can be used elsewhere with only slight modifications and, for the first time, provides a technique to estimate tsunami hazard from volcanic activity, similar to a well-established approach for the estimation of tsunami hazard from earthquake activity.

In moderate-to-low seismic hazard regions, estimating the socio-economic consequences of an earthquake on the regional scale is a costly and difficult task. This study analyses existing global earthquake databases to build a loss flat file of 445 earthquakes since 1967 with a magnitude greater than 4.5. The flat file includes information on the social consequences (e.g. fatalities and injuries) and economic losses (e.g. direct and indirect costs, number of buildings destroyed or damaged). In this study, exposed population and GDP at the date of the earthquake complete the flat file information, estimated thanks to the exposed area computed with an empirical relationship derived from the ground motion footprint provided by USGS ShakeMap. Earthquake consequences have increased since 1967 and follow a non-stationary Poisson distribution with rate proportional to exposure. In order to assess the stationarity of the consequences, we assumed stationary losses and fatalities by normalizing consequences by the exposed wealth and population verified on a sub-set of earthquakes for which exact population is given by national census. The completeness of the flat file catalogue is compared to the international seismological catalogue, and we compute the annual rate of exceedance of human and direct economic losses relative to the exposed population and the associated GDP per capita. We show that, although the number of casualties and the absolute magnitude of losses increase as consequence of urban concentration, global losses, relative to effective exposure corresponding to macroseismic intensity of at least V, decrease. (Access to the flat file: https://www.isterre.fr/philippe-gueguen/earthquake-losses-database/ ).