Network Analysis to Characterize Seismic Ground Motion Variability

Date: 4/24/2019

Time: 06:00 PM

Room: Grand Ballroom

Spatial variability of seismic ground motion plays an important role in earthquake hazard analysis. It has particularly strong impacts on large structures, for which different parts of the foundations may experience different levels of shaking during an earthquake. It also should have a strong influence on the spatial distribution of damage. A better understanding of ground motion spatial correlation would help the guide policy to quantify and mitigate the risks posed by earthquakes

Among previous efforts, Boore et al. (2003), computed spatial correlation of peak ground acceleration (PGA) of the 1994 Northridge earthquake and Jayaram and Baker (2009) characterized PGA residuals from the Northridge earthquake and Chi-Chi earthquakes. However, ground motion in these studies was only sparsely sampled and such that important aspects of spatial correlation were difficult to constrain.

We propose to use the techniques of network analysis to study spatial variability. We treat each station as a node and the whole network as a graph while the link between each pair of nodes is weighted by the similarity between the recorded seismograms. Communities, within which the nodes are strongly correlated, are determined from the graph using community detection algorithms. Community detection allows us to consider the connections beyond individual station pairs, extending to multiple stations that are distributed over wide areas.

We apply the algorithm on the dense array in Long Beach, which had ~100 m station spacing over distances of over five km, which allows us to study the ground motion spatial variability to short scale lengths. We explore the method by varying the selected window length on the seismograms, different earthquakes with varying azimuth and depth, as well as different estimates of signal similarities either in time domain or time-frequency domain. Our detected communities yield reasonable comparisons to the 3D shear wave velocity (Lin et al., 2013) and site amplification (Bowden, 2015) that were independently estimated for the same array.

Presenting Author: Yixiao Sheng

Authors