A Comparison of Methods of Estimating the Attenuation of Earthquake Strong Ground Motion

Strong ground-motion attenuation relations take on a variety of forms, depending upon the parameters used to express the relations and upon the geographic area for which the equations are developed. In general the strong ground-motion parameters, namely acceleration, velocity, displacement and response spectra ordinates, are taken to be proportional to the distance from the earthquake source to the site, to the magnitude or some measure of the strength of the earthquake source, and to loss factors resulting from transmission of energy through the inelastic earth. In certain areas of the world, where strong-motion data are abundant, empirical relations can be developed to express these relations. In other areas of the world, where strong-motion data are few or are entirely lacking, more attention must be given to theoretical considerations. In this paper we give case histories of two such types of regions, namely western North America with an abundance of data and eastern North America with a paucity of data

The tailings dam failure of 5 November 2015 in SE Brazil and its preceding seismic sequence

The collapse of a mine tailings dam and subsequent flood in SE Brazil on 5 November 2015 was preceded by a small-magnitude seismic sequence. In this report, we explore the spatiotemporal associations between the seismic events and the accident and discuss their possible connection. We also analyze the signals generated by the turbulent mudflow, as recorded by the Brazilian Seismographic Network (RSBR). In light of our observations, we propose as possible contributing factor for the dam collapse either ground shaking and/or soil liquefaction triggered by the earthquakes. The possibility of such a small-magnitude earthquake contributing to the collapse of a tailings dam raises important concerns regarding safety and related legislation of dams in Brazil and the world. ©2016. American Geophysical Union.H.A.D. and M.A. acknowledge support from Sao Paulo Research Foundation FAPESP grant 2014/09455-3 and CNPq grant 30.6547/2013-9.Peer reviewe