The Elsinore Fault Zone is one of the three principal right-lateral strands of the San Andreas fault system in southern California, alongside the San Andreas and San Jacinto faults. Running about 180 km from Riverside County through San Diego County (and continuing as the Laguna Salada fault into Mexico), it carries roughly 10% of the Pacific–North American plate motion. Despite its length and its plate-boundary role, it has been by far the quietest of the three major strands in historical time — which is precisely what makes it a concern: it is loaded and has not ruptured in a large earthquake on its main California trace in over a century.
The USGS hazard model splits this fault into 5 sections, each with its own geometry and a geologic slip rate. Each rate says whether it rests on site slip-rate data in the USGS earthquake-geology database or only on the fault’s mapped slip-rate class.
| Section | Movement | Slip rate | Geometry |
|---|---|---|---|
| Elsinore (Coyote Mountains) CA | Right-lateral strike-slip | 3 mm/yr (1–5)site data | dips 82° E · 0–13 km deep |
| Elsinore (Glen Ivy) CA | Right-lateral strike-slip | 5 mm/yr (3–7)site data | vertical · 0–13 km deep |
| Elsinore (Julian) CA | Right-lateral strike-slip | 3 mm/yr (1–5)site data | dips 84° NE · 0–19 km deep |
| Elsinore (Temecula) CA | Right-lateral strike-slip | 5 mm/yr (3–7)site data | vertical · 0–14 km deep |
| Elsinore (stepover) CA | Right-lateral strike-slip | 5 mm/yr (3–7)rate class only | vertical · 0–14 km deep |
Source: USGS NSHM23 fault sections database v3 and western US geologic deformation model v1.0 (on-plane slip rates, preferred with low–high range; site data = measured sites in the NSHM23 earthquake-geology database, rate class only = the fault’s mapped slip-rate category); central US and Cascadia sources from the model’s source files (code.usgs.gov/ghsc/nshmp/nshms/nshm-conus).
The Elsinore has no confirmed historical surface rupture on its main California trace, yet paleoseismology proves it does rupture: trenching at Agua Tibia Mountain (Julian segment) identified five surface-rupturing earthquakes in the past ~4,500 years, the most recent dated between about A.D. 1655 and 1810 (Vaughan, Thorup & Rockwell, 1999). Recurrence is estimated at roughly 250–750 years. A 2025 Los Angeles Times investigation called it a "little-known earthquake fault" that "could unleash devastation across SoCal."
The fault's largest recent events occurred on its southern continuation into Mexico: the 1892 Laguna Salada earthquake (Mw 7.0–7.3) was felt from Santa Barbara to San Quintín and collapsed adobe structures near San Diego, and the 2010 El Mayor–Cucapah earthquake (Mw 7.2) ruptured about 120 km along the Laguna Salada and related faults. On the main California trace, the only M6+ event in the historical record is the 1910 ML 6.0 Temescal Valley earthquake (near the Glen Ivy segment, NW of Lake Elsinore), which caused minor damage and no observed surface rupture.
The Elsinore shares strain with the parallel San Jacinto fault zone through a complex 60–70 km band of stepovers and distributed deformation; slip is partitioned among the three subparallel strands (San Andreas, San Jacinto, Elsinore). The USGS divides the Elsinore into six sections — Whittier, Chino, Glen Ivy, Temecula, Julian, and Coyote Mountain — plus the Laguna Salada section into Mexico. Individual-segment ruptures are modeled at Mw 6.5–7.5, with up to Mw 7.8 for a full multi-segment rupture (UCERF3).
The Elsinore runs through or near fast-growing Corona, Lake Elsinore, Temecula, Murrieta, Julian, and Ocotillo. Its long quiet period on a loaded plate-boundary fault is the reason seismologists watch it. Slip rates and recurrence are estimates with real segment-to-segment variation. See our seismic risk lookup and the California page.