Pulse-like ground motions
Velocity pulses caused mainly by directivity effects have received great deal of attention from engineers and seismologists because of their potential to cause severe damage to structures. In this project we developed algorithms to efficiently identify pulse-like ground motions from large ground-motion databases, developed a comprehensive framework to account for the effects of these pulses in seismic hazard assessment, and proposed a method to explicitly account for these pulses in ground-motion models.
Relevant publications

An Empirically Calibrated Framework for Including the Effects of Near-Fault Directivity in Probabilistic Seismic Hazard Analysis.
Shrey Shahi and Jack Baker (2011)
Bulletin of the Seismological Society of America, 101(2), 742-755.
PDF · E-supplement · Erratum

An Efficient Algorithm to Identify Strong Velocity Pulses in Multi-Component Ground-Motions.
Shrey Shahi and Jack Baker (2013)
Bulletin of the Seismological Society of America.
Under review.

Overview and Comparison of the NGA-West2 Directivity Models.
Paul Spudich, Badie Rowshandel, Shrey Shahi, and Jack Baker (2013)
Earthquake Spectra.
Under review.

Explicit Inclusion of Directivity Effects in Ground-Motion Models.
Shrey Shahi and Jack Baker (2013)
Under preparation.

Final Report of NGA-West2 Directivity Working Group..
Paul Spudich, Jeffery Bayless, Jack Baker, Brian Chiou, Badie Rowshandel, Shrey Shahi, and Paul Sommerville (2013)
PEER Technical Report 2013/09, Berkeley, CA, 131p.
PDF

A Probabilistic Framework to Include the Effects of Near-Fault Directivity in Seismic Hazard Assessment.
Shrey Shahi (2013)
Ph.D. Thesis, Stanford University, Stanford, CA, 226p. (co-published as PEER Technical Report 2013/15)
PDF · E-Supplement · PEER Report (PDF)

Directivity Models Produced for the Next Generation Attenuation West 2 (NGA-West 2) Project.
Paul Spudich, Jenny Watson-Lamprey, Paul Somerville, Jeff Bayless, Shrey Shahi, Jack Baker, Badie Rowshandel, and Brian Chiou (2012)
15th World Conference on Earthquake Engineering, Lisbon, Portugal, 9p.
PDF

Regression Models for Predicting the Probability of Near-Fault Earthquake Ground Motion Pulses, and their Period.
Shrey Shahi and Jack Baker (2011)
11th International Conference on Applications of Statistics and Probability in Civil Engineering, Zurich, Switzerland, 8p.
PDF

Signal Processing and Probabilistic Seismic Hazard Analysis Tools for Characterizing the Impact of Near-Fault Directivity.
Shrey Shahi and Jack Baker (2010)
Proceedings, 7th International Conference on Urban Earthquake Engineering (7CUEE) & 5th International Conference on Earthquake Engineering (5ICEE), Tokyo, Japan, 6p.
PDF

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Ground-motion directionality
Structures in seismically active regions are generally designed considering ground motion in the horizontal plane. However, the acceleration response spectrum, which is the intensity measure used for design, is defined to represent a single component of the ground-motion. The NGA-West2 ground-motion models predict the median intensity over all orientations ($$Sa_{RotD50}$$), while some structural engineers want to use maximum intensity over all orientations ($$Sa_{RotD100}$$). In this project we developed empirical models to convert the $$Sa_{RotD50}$$ to $$Sa_{RotD100}$$ to allow consistent use of ground-motion intensity in the design process, modeled the probability distribution of the orientations in which the maximum occurs, modeled the relationship between the maximum orientation of Sa at different periods, and proposed methods to compute alternate target spectra expected to be observed in a particular orientation or in the orientation in which $$Sa_{RotD100}$$ is observed at a particular period.
Relevant publications

NGA-West2 Models for Ground-Motion Directionality.
Shrey Shahi and Jack Baker (2013)
Earthquake Spectra.
Accepted for publication.

NGA-West2 Models for Ground-Motion Directionality.
Shrey Shahi and Jack Baker (2013)
PEER Technical Report 2013/10, Berkeley, CA, 46p.
PDF

Preliminary NGA-West2 Models for Ground-Motion Directionality.
Shrey Shahi and Jack Baker (2012)
15th World Conference on Earthquake Engineering, Lisbon, Portugal, 10p.
PDF

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Uncertainty in ground-motion intensity predictions
Ground-motion intensity from future earthquakes are generally predicted using ground-motion models. The error in ground-motion intensity prediction can stem from source, site, or path effects not accounted for by the ground-motion model. Some of this error is repeatable, for example error in prediction due to any site effect not captured by the model can be expected to be repeated in future earthquake. Knowledge of these repeatable errors can help improve the site specific estimated of seismic hazard. In this project we have compiled a database of earthquake ground motions recorded in different regions of the world. We plan to split the error in prediction from the models into source, site, and path errors and study their properties across different regions and magnitude ranges.
Details will be available soon

This is an ongoing project and publications will be added soon. Check back later.

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