Understanding single-station ground motion variability and uncertainty (sigma) – Lessons learnt from EUROSEISTEST

Accelerometric data from the well-studied valley EUROSEISTEST are used to investigate ground motion uncertainty and variability. We define a simple local ground motion prediction equation (GMPE) and investigate changes in standard deviation (σ) and its components, the between-event variability (τ) and within-event variability (φ). Improving seismological metadata significantly reduces τ (30-50%), which in turn reduces the total σ. Improving site information reduces the systematic site-to-site variability, φS2S (20-30%), in turn reducing φ, and ultimately, σ. Our values of standard deviations are lower than global values from literature, and closer to path-specific than site-specific values. However, our data have insufficient azimuthal coverage for single-path analysis. Certain stations have higher ground-motion variability, possibly due to topography, basin edge or downgoing wave effects. Sensitivity checks show that 3 recordings per event is a sufficient data selection criterion, however, one of the dataset’s advantages is the large number of recordings per station (9-90) that yields good site term estimates. We examine uncertainty components binning our data with magnitude from 0.01 to 2 s; at smaller magnitudes, τ decreases and φSS increases, possibly due to κ and source-site trade-offs Finally, we investigate the alternative approach of computing φSS using existing GMPEs instead of creating an ad hoc local GMPE. This is important where data are insufficient to create one, or when site-specific PSHA is performed. We show that global GMPEs may still capture φSS, provided that: 1. the magnitude scaling errors are accommodated by the event terms; 2. there are no distance scaling errors (use of a regionally applicable model). Site terms (φS2S) computed by different global GMPEs (using different site-proxies) vary significantly, especially for hard-rock sites. This indicates that GMPEs may be poorly constrained where they are sometimes most needed, i.e. for hard rock

Data for: Empirical Seismic Fragility Functions based on Field Survey Data after the 5 May 2014 Mae Lao (Northern Thailand) Earthquake

, Building DamageDatabase following Mae Lao earthquake, 2014 (in Thai) prepared by Department of Public Works and Town & Country Planning (DPT)THIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV

Probabilistic Seismic Hazard Macrozonation of Tamil Nadu in Southern India

The south Indian state of Tamil Nadu in the peninsular shield is a zone of low to moderate seismic activity with a sparse historical record of significant earthquakes. The current intensity-based zoning adopted by the Indian seismic code stipulates an effective peak ground acceleration (PGA) of either 0.10 or 0.16g for different parts of the state, for the maximum considered earthquake (MCE), and the service life of a structure. In the current study, probabilistic seismic hazard contour maps for Tamil Nadu and the union territory of Pondicherry, in terms of the ground-motion parameters, PGA and spectral accelerations, at 0.1, 0.5, and 1.0 sec for 2%, 5%, and 10% probabilities of exceedance in a 50 yr period, have been produced. Hazard computations have been performed over a grid of sites covering the territory at an interval of 0.2°. A comprehensive earthquake catalog has been compiled for the region extending between 2 and 20.7° N latitude and 68 and 88° E longitude and spanning ∼950 yrs. The hazard maps are produced by suitably accounting for epistemic uncertainty in the hazard computations within a logic-tree framework incorporating parameters such as different probabilistic hazard analysis methods (classical Cornell–McGuire and zone-free approaches), catalog completeness estimation methods, maximum cutoff magnitude, and ground-motion predictive equations for shallow crustal intraplate environments. The hazard maps are compared to the zoning prescribed by the seismic code. The current estimations show that the potential seismic hazard in considerable parts of the state is underestimated by the broad zoning adopted by the Indian Standards

Development of the Global Earthquake Model’s neotectonic fault database

The Global Earthquake Model (GEM) aims to develop uniform, openly available, standards, datasets and tools for worldwide seismic risk assessment through global collaboration, transparent communication and adapting state-of-the-art science. GEM Faulted Earth (GFE) is one of GEM’s global hazard module projects. This paper describes GFE’s development of a modern neotectonic fault database and a unique graphical interface for the compilation of new fault data. A key design principle is that of an electronic field notebook for capturing observations a geologist would make about a fault. The database is designed to accommodate abundant as well as sparse fault obser- vations. It features two layers, one for capturing neotectonic faults and fold observations, and the other to calculate potential earthquake fault sources from the observations. In order to test the flexibility of the database structure and to start a global compilation, five preexisting databases have been uploaded to the first layer and two to the second. In addition, the GFE project has characterised the world’s approximately 55,000 km of subduction interfaces in a globally consistent manner as a basis for generating earthquake event sets for inclusion in earthquake hazard and risk modelling. Following the subduction interface fault schema and including the trace attributes of the GFE database schema, the 2500-km-long frontal thrust fault system of the Himalaya has also been characterised. We propose the database structure to be used widely, so that neotectonic fault data can make a more complete and beneficial contribution to seismic hazard and risk characterisation globally