Harvard Seismology: Event Location


 This project is currently funded by the Defense Threat Reduction Agency (DTRA) with the goal of achieving high precision regional and teleseismic event locations using 3D models of mantle structure.  Primary motivation for the research is successful monitoring of the proposed Comprehensive Test Ban Treaty (CTBT).  The CTBT has the stated goal of locating events to a precision greater than 1000 km2.  This goal is frequently not obtained using conventional 1-D seismic velocity models and location techniques. Obtaining better quality teleseismic event locations is also important for studies which utilize the global distribution of seismicity, particularly in terms of depth.

Previously, we  have demonstrated that absolute locations determined using teleseismic arrival times can be improved through incorporation of three dimensional (3-D) models of the P-wave velocity structure of the mantle, even when these models are parameterized by a low-order expansion of the velocity heterogeneity in terms of spherical harmonics.  In addition, a global  study of Pn arrivals reported to the ISC indicates that azimuthal anisotropy is an important feature in upper mantle P-velocities.  This has important implications for the accuracy at which events can be located at regional distances.

Currently our research is focused in five main areas:

  1. 1. Development of new techniques for improving current Earth models, such as multiple resolution algorithms and incorporation of regional seismic phases.
  2. 2. Construction of higher resolution three-dimensional Earth models, with emphasis on P-wave structure.
  3. 3. Evaulation of the new models using independent data.
  4. 4. Development of additional station and/or path corrections, in conjunction with the 3D models, for use in location algorithms.
  5. 5. Compilation of a high quality dataset of well located master events, including both explosions and earthquakes, for use in assessing improvements in location capability.

Current participants in this project are

Michael Antolik, Göran Ekström, Adam Dziewonski, Yu J. Gu, Lapo Boschi, Jianfeng Pan,

Dr. Ivan Kitov, Institute for the Dynamics of the Geosphere, Moscow


Previous Results

Recent Developments


Title Illustration. P-wave travel time residuals in 5o x 5o caps predicted by the mantle model S&P12/WM13 for an event in Kermadec. Red and blue triangles denote positive and negative residuals, respectively.

Michael Antolik, Department of Earth and Planetary Sciences, Harvard University, copyright ©1998 all rights reserved