Overview

On June 29-30, 2025, UC Santa Barbara will host a field trip and workshop to mark the centennial of the 1925 M6.5 Santa Barbara earthquake (https://eq25.org/). The goal is to bring together researchers from different disciplines of earthquake science to discuss results on this and later events, and to assess earthquake and tsunami hazards in this densely populated area. Previously, in 2012, SCEC established the Ventura Special Fault Study Area (SFSA) to promote interdisciplinary research on the potential for large, damaging earthquakes in this region. This centennial provides a unique and timely opportunity to re-evaluate and integrate new data, observations, and models related to this significant historical and later events, and the associated hazard potential from the active fault systems responsible for this seismicity. On June 30, we will host an in-person workshop to explore key science questions (see below), preceded by a half-day field trip on June 29, the earthquake’s centennial anniversary. Researchers from earthquake geology, seismology, geodesy, numerical modeling and working on the active fault and fold systems in the region are invited to apply. Limited travel support is available, and in-person participation is capped at 35 people. Applicants not accepted will receive a link to watch the workshop presentations online. Key science questions we hope this workshop and field trip will address include:

1. What are the primary, first-order data and observations that any model for the unusual patterns of uplift and differential subsidence, and the 3D subsurface fault geometry and strain must satisfy?
2. What are the proper criteria to evaluate, validate and discriminate between competing fault models and model assumptions used to assess the inferred hazard potential in this area?
3. What are the likely source faults for Santa Barbara-Ventura area seismicity (including 1925, 1941, 1978 and 2013 earthquakes), and how do these faults relate to the fault architecture driving Western Transverse Ranges deformation? To what extent is this deformation elastic?
4. What can dynamic rupture models tell us about the ground motions, and surface and seafloor displacements expected for a repeat of 1925 or a much larger M7.4+ regional earthquake?
5. What is the pattern of Holocene surface and seafloor uplift and fault displacement, and is this pattern driven primarily by N-dipping or S-dipping faults, or some complex combination?
6. Is the unusual uplift at Pitas Point representative of slip farther along strike (and thus large magnitude earthquakes), or is it local and anomalous (and reflects some other process)?
7. Are the major active fault systems fundamentally detached and if so, what is the dip and depth of this detachment? If not, how is fault geometry more accurately modeled in 3D?
8. What does the presence of a line of Precariously Balanced Rocks behind Santa Barbara and Montecito [Brune, 2009] tell us about the maximum magnitudes and ground motions the active faults can produce?