Quantitative Classification of Near-Fault Ground Motions Using Wavelet Analysis

Abstract

A method is described for quantitatively identifying ground motions containing strong velocity pulses, such as those caused by near-fault directivity. The approach uses wavelet analysis to extract the largest velocity pulse from a given ground motion. The size of the extracted pulse relative to the original ground motion is used to develop a quantitative criterion for classifying a ground motion as "pulselike." The criterion is calibrated by using a training data set of manually classified ground motions. To identify the subset of these pulselike records of greatest engineering interest, two additional criteria are applied: the pulse arrives early in the ground motion and the absolute amplitude of the velocity pulse is large. The period of the velocity pulse (a quantity of interest to engineers) is easily determined as part of the procedure, using the pseudoperiods of the basis wavelets. This classification approach is useful for a variety of seismology and engineering topics where pulselike ground motions are of interest, such as probabilistic seismic hazard analysis, groundmotion prediction ("attenuation") models, and nonlinear dynamic analysis of structures. The Next Generation Attenuation (NGA) project ground motion library was processed using this approach, and 91 large-velocity pulses were found in the faultnormal components of the approximately 3500 strong ground motion recordings considered. It is believed that many of the identified pulses are caused by near-fault directivity effects. The procedure can be used as a stand-alone classification criterion or as a filter to identify ground motions deserving more careful study.

Near -Source Pulse-Like Seismic Demand for Multi-Linear Backbone Oscillators

“…Having as a starting point the dataset used in [9], the pulse identification approaches suggested in [10] and [11] were used to seek out additional directivity ground motions. This search mainly focused on more recent seismic events which provided a multitude of NS recordings, such as the Parkfield 2004 (California) event, the Darfield 2010 and Christchurch 2011 (New Zealand) events and the South Napa 2014 (California) event.…”

Consideración de los pulsos de velocidad en el diseño de estructuras con aislamiento sísmico de base

“…El conjunto de registros utilizados, son catalogados como registros de campo cercano (near-fault) tipo impulsivo según el criterio de clasificación J. Baker (2007) y presentan claros pulsos en la historia de tiempo de las velocidades. La tabla 1 muestra los parámetros de la fuente sísmica y la estación seleccionada para analizar los registros.…”

Would RC wide-beam buildings in Spain have survived Lorca earthquake (11-05-2011)?

“…I D accounts broadly for velocity pulses content; small / big values of I D correspond to records with / without pulses. PI is pulse index [Baker 2007], which ranges between 0 and 1; records with scores above 0.85 and below 0.15 are classified as pulses and non-pulses, respectively. E p is relative pulse energy [Zhai et al 2013], representing portion of ground motion energy that corresponds to pulse; pulse is extracted by peak-point method [Dickinson, Gavin 2011].…”