Location

San Diego, California

Session Start Date

3-26-2001

Session End Date

3-31-2001

Abstract

We present two new techniques for treating earthquake intensity data objectively and reproducibly. First, our natural-neighbor, n-n, isoseismals (program: ConVor) are used to draw objective and reproducible isoseismals of the Whittier Narrows ML=5.9, 1987 earthquake from the earthquake damage (“felt reports”) sparsely observed in the region by the U.S.G.S. ConVor uses the n-n coordinates to weight and interpolate the observations; thus, the weights of the experimental sites which are natural neighbors to a new point are proportional to the areas of the intersections of their Voronoi polygons. It is shown that the n-n isoseismals: 1) honour the experimental data completely, and are, thus, frequency-complete representations; 2) are easy-to-grasp and reliable overviews of regional earthquake damage; 3) do not ballast any subsequent quantitative treatment, because they do not introduce new (contouring) parameters. Secondly, we demonstrate that the approximate source geometry and kinematics of this earthquake can be back-predicted by inverting its intensity data automatically. The inversion involves twelve parameters, the most sensitive of which are the epicentral co-ordinates and the fault plane solution; our trial-and-error technique minimizes the sum of the squared residuals (calculated intensity - minus - observed intensity) at the surveyed sites, and the errors of the source parameters are also estimated.

Department(s)

Civil, Architectural and Environmental Engineering

Appears In

International Conferences on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics

Meeting Name

Fourth Conference

Publisher

University of Missouri--Rolla

Publication Date

3-26-2001

Document Version

Final Version

Rights

© 2001 University of Missouri--Rolla, All rights reserved.

Document Type

Article - Conference proceedings

File Type

text

Language

English

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Mar 26th, 12:00 AM Mar 31st, 12:00 AM

New-Generation Objective and Reproducible Isoseismals, and Tests of Source Inversion of the USGS "Felt Reports"

San Diego, California

We present two new techniques for treating earthquake intensity data objectively and reproducibly. First, our natural-neighbor, n-n, isoseismals (program: ConVor) are used to draw objective and reproducible isoseismals of the Whittier Narrows ML=5.9, 1987 earthquake from the earthquake damage (“felt reports”) sparsely observed in the region by the U.S.G.S. ConVor uses the n-n coordinates to weight and interpolate the observations; thus, the weights of the experimental sites which are natural neighbors to a new point are proportional to the areas of the intersections of their Voronoi polygons. It is shown that the n-n isoseismals: 1) honour the experimental data completely, and are, thus, frequency-complete representations; 2) are easy-to-grasp and reliable overviews of regional earthquake damage; 3) do not ballast any subsequent quantitative treatment, because they do not introduce new (contouring) parameters. Secondly, we demonstrate that the approximate source geometry and kinematics of this earthquake can be back-predicted by inverting its intensity data automatically. The inversion involves twelve parameters, the most sensitive of which are the epicentral co-ordinates and the fault plane solution; our trial-and-error technique minimizes the sum of the squared residuals (calculated intensity - minus - observed intensity) at the surveyed sites, and the errors of the source parameters are also estimated.