Under this proposal we will develop, test, and document new methodologies for creating probability density functions (PDFs)of first-arriving and secondary seismic phases from datasets of seismic phase arrival times and hypocenters. Algorithms will be developed to use seismic phase PDFs in standard earthquake location procedures in the context of phase association and weighting. Tests will be conducted to determine the magnitude of difference in location parameters relative to traditional methods, emphasizing data at regional distances. Seismic phase PDFs will be tested as an indicator of heterogeneity in different regions. Results of this work are expected to lead to improved algorithms for seismic source localization, especially in suport of the U.S. nuclear monitoring program for which statistical rigor of results has a high priority. Bias in hypocenters and their uncertainties will be reduced. The same benefits will be propagated to earthquake data centers, improving their ability to carry out earthquake monitoring and hazard reduction programs.
