Ground-Motion Intensity Measure Correlations on Interface and Intraslab Subduction Zone Earthquakes Using the NGA-Sub Database

ABSTRACT The NGA-Sub (subduction zone earthquake) database developed by the Pacific Earthquake Engineering Research center is used to derive new correlation coefficients for a number of ground-motion intensity measure (IM) parameters from ground motions in subduction zone earthquakes, considering both interface and intraslab tectonic settings. The IMs include peak ground acceleration, pseudospectral accelerations with periods from 0.01 to 10 s, Arias intensity, cumulative absolute velocity, peak ground velocity, and significant duration. Comparisons of the estimated correlation coefficients for ground motions from the interface and intraslab tectonic settings generally show a good agreement. Our estimations are also in good agreement with correlation coefficients estimated in previous studies that used ground motions from shallow crustal earthquakes, supporting the concept that any variation in correlation coefficients comes from spectral shape (i.e., the distribution of peaks and troughs) rather than tectonic region. This study also explores the influence of parameters such as magnitude, distance, and site conditions on the estimated correlation coefficients. We did not find apparent trends of the correlation coefficients with respect to these parameters. Finally, we propose analytical models to estimate correlation coefficients between the IMs explored in this study, considering both subduction interface and intraslab tectonic settings.

70%-Damped Spectral Acceleration as a Ground Motion Intensity Measure for Predicting Highly Nonlinear Response of Structures

We investigate 70%-damped spectral acceleration, Sa70%( T), as a ground motion intensity measure for predicting maximum interstory drift ratios of 0.03, 0.06, and 0.1 as well as collapse. We perform incremental dynamic analysis with 50 ground motions on 22 steel moment frame building models with heights of 3, 9, and 20 stories. We find that if T1 ≤ T ≤ 2 T1, Sa70%( T) is efficient and usually sufficient for the considered levels of highly nonlinear response. Sa70%(1.5 T1) is generally an efficient choice. We find that Sa70%( T) is similar to average spectral acceleration, Saavg, in many ways, as both intensity measures emphasize a wide range of periods in a ground motion when compared to Sa5%( T1). Sa70%( T) is equivalent to the peak of a ground motion's low-pass filtered acceleration, and this interpretation may be useful for estimating the potential of a ground motion to elicit a highly nonlinear response.