NESS1: A Worldwide Collection of Strong‐Motion Data to Investigate Near‐Source Effects

Abstract

The availability of high‐quality waveforms recorded in epicentral areas of moderate‐to‐strong earthquakes is a key factor for investigating ground‐motion characteristics close to the seismic source. In this study, near‐source strong‐motion waveforms (named NESS1) were collected from worldwide public archives with the aim of building a flat file of high‐quality metadata and intensity measures (IMs) of engineering interest. Particular attention was paid to the retrieval of reliable information about event sources, such as geometries and rupture mechanisms that are necessary to model near‐source effects for engineering seismology and earthquake engineering applications. The accelerometric records are manually and uniformly processed, and the associated information is fully traceable. NESS1 consists of about 800 three‐component waveforms relative to 700 accelerometric stations, caused by 74 events with moment magnitude larger than 5.5 and hypocentral depth shallower than 40 km, with Joyner–Boore distance up to 140 km. Ground‐motion data were selected to have a maximum source‐to‐site distance within one fault length, defined through seismological scaling relations. About 40 records exhibit peak acceleration or peak velocity exceeding 1g or 120cm/s ⁠, and they represent some of the largest ground motion ever recorded. Evidence of near‐source effects was recognized in the NESS1 dataset, such as velocity pulses, large vertical ground motions, directional and hanging‐wall amplifications and fling step. In particular, around 30% of the records was found to exhibit pulse‐like characteristics that are possibly due to forward rupture directivity.