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Improving First-order Seismic Characterization Through Calibrated Earthquake Locations

Description: 

Accurate earthquake locations are foundational to seismic research and rapid hazard assessment. Despite being a well-established inverse problem, earthquake location estimates remain inherently complex due to factors such as unknown Earth structure, phase-pick uncertainties, and inconsistencies in station distributions. Single-event location methods are computationally more efficient, but they often suffer from significant inconsistencies introduced by these limitations. In contrast, multiple-event location techniques leverage statistical relationships among events to better estimate hypocenter uncertainties and address inconsistencies from poor network configurations. However, multiple-event methodologies still suffer from location bias due to unknown velocity structure, typically several km when using local observations and >10km when using regional/teleseismic observations.

We highlight the application of MLOC, a specialized multi-event earthquake location procedure, in generating the Global Catalog of Calibrated Earthquake Locations (GCCEL), which is updated and published online by the USGS. This catalog includes ~28,000 hypocenters in 366 event clusters that are geographically well-distributed, leveraging global and local networks, as well as temporary deployments where available. Calibrated hypocenters are minimally biased by unknown Earth structure due to careful selection of data at short epicentral distances for estimating the absolute locations and procedures to minimize misfit of the local velocity model, while the associated hypocentral parameter uncertainties are fully quantified with empirically determined data variances. GCCEL serves as a benchmark dataset, supporting improvements in routine earthquake monitoring and advanced seismic research, including development of 3D and regional specific velocity models and improved statistical frameworks for seismic monitoring. This presentation will emphasize the importance of calibrated locations and the challenges of absolute location accuracy, demonstrating how GCCEL could address these complexities to enhance first-order seismic observations.

Session: Advances in Reliable Earthquake Source Parameter Estimation - I

Type: Oral

Date: 4/16/2025

Presentation Time: 08:30 AM (local time)

Presenting Author: Ezgi

Student Presenter: No

Invited Presentation: Yes

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