Rapid-response Seismic Imaging of the Aftershock Sequence of the 14 April 2025 Mw 5.2 Julian Earthquake
On 14 April 2025, an Mw 5.2 earthquake occurred ~5 km south of Julian, California, within the Peninsular Ranges between the Elsinore and San Jacinto fault systems. The event triggered a rapid-response seismic deployment aimed at capturing the early aftershock sequence in a structurally complex fault corridor. Beginning on 16 April, within 48 hours of the mainshock, we installed a dense temporary array to understand the fault geometry and aftershock behavior that are relatively poorly resolved by the standard regional catalog made using conventional methods. In total, we deployed 36 nodal seismometers (SmartSolo IGU-16HR 3C 5 Hz) to augment the permanent network, achieving near-complete azimuthal coverage around the mainshock and recording approximately one month of continuous data.
Using these data, we constructed an AI-based earthquake catalog using AI-PAL (Zhou et al., 2025), a streamlined workflow that first builds a rule-based seed catalog and then trains a transformer-based phase detector to scan continuous waveforms, integrating nodal and SCEDC stations. The resulting catalog contains approximately 1,200 earthquakes, representing a sixfold increase relative to the standard SCSN catalog, and reduces the magnitude of completeness by ~0.2. Relocated events and cross-sectional imaging will reveal fine-scale fault geometry and improved delineation of seismicity patterns not resolved in the conventional catalog. Spatiotemporal analyses will further resolve aftershock clustering and migration, providing new constraints on fault structure and potential effect on the Elsinore fault ~7 km northeast of the epicenter. These results will demonstrate that dense temporary deployments combined with AI-based detection substantially improve earthquake catalogs and fault imaging in structurally complex regions, even over short recording intervals.
Session: Southern California Seismicity: Past, Present and Future [Poster]
Type: Poster
Room: Exhibit Hall A+B
Date: 4/17/2026
Presentation Time: 08:00 AM (local time)
Presenting Author: Binayak Parida
Student Presenter: Yes
Invited Presentation:
Poster Number: 155
Additional Authors
Binayak Parida Presenting Author bpari004@ucr.edu University of California, Riverside |
Abhijit Ghosh Corresponding Author aghosh@ucr.edu University of California, Riverside |
Shankho Niyogi shankho.niyogi@email.ucr.edu University of California, Riverside |
Heather Ford heather.ford@ucr.edu University of California, Riverside |
Guadalupe Bravo lupita.bravo@email.ucr.edu University of California, Riverside |
Rebecca Leung rleung@ucr.edu University of California, Riverside |
Adam Margolis adam.margolis@email.ucr.edu University of California, Riverside |
Shiori Nakaya snaka047@ucr.edu University of California, Riverside |
Axel Periollat axelp@ucr.edu University of California, Riverside |
Ashley Stroup astro019@ucr.edu University of California, Riverside, Riverside, California, United States |
Rapid-response Seismic Imaging of the Aftershock Sequence of the 14 April 2025 Mw 5.2 Julian Earthquake
Category
Southern California Seismicity: Past, Present and Future
Description