The Newport–Inglewood Fault Zone is one of the highest-consequence urban faults in the United States. Its surface trace — a line of hills and en-echelon folds — runs directly beneath the densely built Los Angeles–Long Beach corridor (Culver City, Inglewood, Compton, Signal Hill, Long Beach, Huntington Beach, Newport Beach), then continues offshore and, as the Rose Canyon segment, straight through central San Diego (La Jolla, Old Town, downtown, San Diego Bay). It is largely buried: the 1933 earthquake ruptured about 9 miles deep with no surface rupture.
The USGS hazard model splits this fault into 3 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 |
|---|---|---|---|
| Newport - Inglewood CA | Right-lateral strike-slip | 1 mm/yr (0.5–3)site data | vertical · 0–15 km deep |
| Newport - Inglewood (offshore) CA | Right-lateral strike-slip | 1 mm/yr (0.5–3)rate class only | vertical · 0–10 km deep |
| Rose Canyon CA | Right-lateral strike-slip | 2 mm/yr (1–5)site data | vertical · 0–7.7 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).
On March 10, 1933, a M6.4 earthquake struck the Newport–Inglewood fault, its epicenter about 3 miles south of Huntington Beach at roughly 8 miles depth. About 120 people died, mostly in the collapse of unreinforced masonry — 70 schools were destroyed and 120 more heavily damaged. The disaster literally changed how California builds: it triggered the Field Act (seismic standards for K-12 schools) and the Riley Act (requiring local building regulation). It remains the deadliest southern California earthquake of the 20th century, at a time of far smaller population.
The fault slips right-laterally at an estimated ~0.5–2.4 mm/yr (varying by segment and method). It is highly segmented (seven sections in the USGS database), and its surface expression is folds and hills rather than a clean scarp. The USGS runs formal M6.8 (Newport–Inglewood) and M6.9 (Rose Canyon) scenarios precisely because a repeat of 1933 today, under modern population, would be catastrophic.
Research (Sahakian et al., 2017) found that Newport–Inglewood and Rose Canyon are actually one continuous fault system from San Diego Bay to Seal Beach, capable of a M7.3–7.4 earthquake; ruptures can jump gaps of 2 km or less. Rose Canyon's most recent large surface rupture was in the mid-1700s (previous ~A.D. 1300), on a roughly 700-year late-Holocene cycle (Singleton et al., 2019). A USGS–CGS model includes the potential for rupture of the entire zone in a M7.5 earthquake.
The 1933 earthquake's legacy — California's seismic building codes — began on this fault. Today it underlies millions of people across LA, Orange, and San Diego counties. See the California page and our seismic risk lookup.