SCEC Award Number 25154 View PDF
Proposal Category Collaborative Research Project (Multiple Investigators / Institutions)
Proposal Title Joint Characterization of Transient Deformation and Repeating Earthquakes in California
Investigator(s)
Name Organization
Junle Jiang University of Oklahoma Taka'aki Taira University of California, Berkeley
SCEC Milestones A1-2, A3-5, B2-2, D1-1 SCEC Groups Geodesy, SDOT, FARM
Report Due Date 03/15/2026 Date Report Submitted 05/07/2026
Project Abstract
 Fault zones display a spectrum of slip behavior, including wave-producing earthquake ruptures lasting seconds to minutes and slower movements spanning hours to months or longer. Several fault segments in California are well known for their seismic and aseismic behaviors monitored by diverse geophysical networks. While seismological approaches illuminate earthquake processes and fault structures, complementary geodetic instruments measure ground displacement, crustal strain, and surface creep. Recent studies have revealed complex relationships between transient aseismic faulting and coincident seismicity, highlighting spatiotemporal observational gaps and variability across geological settings. In this SCEC project, we have compiled datasets and investigated a diverse range of transient deformation, surface creep, and fault slip, along with characteristically repeating earthquakes in selected regions across California. Our study areas include major segments (San Juan Bautista, Parkfield) of the San Andreas Fault, Superstition Hills Fault, San Jacinto Fault, and the Salton Sea. Building upon geodetic data products from prior SCEC projects, we have analyzed geodetic observations of transient deformation (creepmeters, strainmeters, and GNSS) and CRE-based fault slip histories in these priority regions, determined the characteristic amplitudes and timescales of these transients, and evaluated cross-region variabilities, toward a systematic analysis of full datasets. To better characterize fault slip inferred from CREs, we have also updated the CRE catalog up to the end of 2025 in northern California faulting systems (Hayward, Parkfield). Our analysis reveals distinct temporal behaviors of aseismic transients attributed to (1) creeping vs seismogenic faults, (2) spontaneous, triggered, and postseismic modes, and (3) factors of source depths and instrumental apertures.
SCEC Community Models Used Community Fault Model (CFM), Community Geodetic Model (CGM)
Usage Description CFM is used to characterize fault zone geometry and compare with sources of transient deformation and seismicity. CGM provides estimates of long-term secular deformation rates.
Intellectual Merit Our research contributes to building integrated multi-sensor datasets for studying transient faulting processes in California. The observations and analyses for representative regions reveal the spatiotemporal complexity and regional variability of seismic-aseismic faulting. The integrated analyses can help validate physical models of faulting and inform the development of effective rheology laws and earthquake forecasts. The comparison, characterization, and integration of diverse geodetic datasets will help advance Community Geodetic Models as it aims to incorporate detailed spatial/temporal information.
Broader Impacts The project supports an early-career tenure-track faculty member and the training of a 2nd-year graduate student in compiling and analyzing geodetic datasets, which benefits his dissertation project. The project has supported and enhanced the collaborations of the PIs across two institutions. The diverse range of observations and transient fault system phenomena has been an important topic of PIs’ education and outreach activities.
Project Participants PI Junle Jiang and graduate student Zhenyu Kang (The University of Oklahoma) and PI Taka’aki Taira (UC Berkeley) have worked on different tasks of the project. Some project topics (geodetic monitoring) have been incorporated into outreach activities that Jiang has done at Westmoore High School in Oklahoma.
Exemplary Figure Figure 2. Characterizing transient creep events at different sites. (a, d, j) Fault slip histories during transient creep events at CWN (SJB), XGH (Parkfield), and coSH (SHF). (g) Postseismic creep after the 2004 Parkfield earthquake at different creepmeters. (b, e, h, k) Logarithmic function fits of transient slip. (c, f, i, l) Effective amplitude vs timescale for each record. Colors indicate different (a, d, j) creep events or (g) creepmeters, consistent across three rows.
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