Data resources for NGA-subduction project

A relational database was developed over a five-year period to support ground motion model (GMM) development for the Next Generation Attenuation-Subduction (NGA-Sub) project. The relational database has components that interact according to a database schema, including a source and path component used to describe attributes of seismic sources in global subduction regions and to compute source-to-site distances, a site component that describes attributes of sites where recordings have been made, and a ground motion component.

The source component of the database has information for 1880 earthquakes, mainly from the following regions: the Pacific Northwest region of North America, Alaska and the Aleutian Islands, Japan, Taiwan, New Zealand, South America, Central America, and Mexico. Of the 1880 earthquakes, 88 have finite fault models (FFMs) from the literature that were systematically reviewed, distilled to one more rectangular shapes, and trimmed according to procedures based on percentage of total slip. For earthquakes without FFMs, a simulation routine is used to represent finite fault effects required for distance calculations. This simulation routine was adjusted and made more uniform in its application than in prior NGA projects. All earthquakes are classified as interface, intraslab, shallow crustal, or outer rise, using uniform protocols developed for this project. All earthquakes are also assigned class designations adapted from a prior NGA project for active regions, that allows foreshock, mainshock, and aftershock events to be distinguished.

The site component of the database is described in a companion paper (Ahdi et al. 2020 [1]).

The ground motion component of the database consists of median – and maximum – horizontal component peak parameters (peak ground acceleration, PGA and peak ground velocity, PGV) and pseudo-spectral accelerations (PSa) at 111 oscillator periods and 11 damping ratios. Response spectra were also computed for the vertical component. Fourier amplitude spectra (FAS) and duration metrics were also computed. The ground motion recordings were obtained from collaborating organizations world-wide as uncorrected (Vol 1) digital recordings, that were corrected (componentspecific low – and high – pass filters and baseline correction, as needed) following Pacific Earthquake Engineering Research Center (PEER)/NGA protocols.

The relational database operates on each of these (and other) database components to dynamically draw relevant parameters into a single file, known as a flatfile, that is used by researchers engaged in GMM development. The flatfiles used in model development are being published with the NGA-Sub GMMs as products of the NGA-Sub project.