QuakeIndex

Fault · California

North Frontal thrust system

67 kmlong (42 mi), as mapped
0.2–1 mm/yrhow fast it slips
< 15,000 yearssince it last broke the surface
36quakes of M2.5+ within 10 km since 2016

In plain English

The two sides move 0.2 to 1 mm a year — 2 to 10 cm every century.

Its most recent surface rupture is younger than 15,000 years.

The largest earthquake recorded near it was M 6.4 in 1899 (Cajon Pass area, northwest of San Bernardino, California) — about 110,000 times the energy of an M3.0, the size people start to feel. It released about 52 kilotons of TNT.

USGS maps it as 2 sections: Eastern section, Western section.

This week vs. its last ten years

85/100

elevated

1 quake of M1.5+ within 5 km of the trace in the last 7 days — busier than 85% of weeks since 2016. A normal week: 0–0.

Computed from the USGS catalogue · a description of the past, not a forecast · method

San Andreas faultElsinore faultGarlock faultSan Jacinto faultNewport-Inglewood-Rose Canyon faultLenwood-Lockhart faultHelendale-South Lockhart faultSan Gabriel faultSierra Madre faultCalico-Hidalgo faultPisgah-Bullion faultCamp Rock-Emerson-Copper Mountain faultPinto Mountain fault (includes Morongo Valley fault)Harper faultBlackwater faultJohnson Valley faultLavic Lake faultMesquite Lake faultSan Gorgonio Pass faultBullion Mountains faultManix faultHomestead Valley faultCleghorn faultIndio Hills Fault ZoneBurnt Mountain faultCrafton Hills faultCoachella Fan Fault ZoneMt. General faultBanning faultEureka Peak faultLong Canyon faultOld Woman Springs faultRed Hill-Etiwanda Avenue faultBeaumont Plain fault M 6.4 · 1899 · Cajon Pass area, northwest of San Bernardino, California M 6.0 · 1858 · Near San Bernardino, California
The North Frontal thrust system as mapped at the surface (glowing), with the other mapped faults nearby, 36 of the M2.5+ earthquakes within 10 km of it since 2016 (dots), and the epicentres of the large historic earthquakes recorded near it (rings). Traces: USGS Quaternary Fault and Fold Database. Historic epicentres are estimates.

Every year since 2016

Earthquakes of M2.5+ with an epicentre within 10 km of the mapped trace. Near is not the same as on: some will have slipped on neighbouring faults.

The big ones recorded near it

  1. M 6.4 Cajon Pass area, northwest of San Bernardino, California
    July 22, 1899 · epicentre 23 km from the trace
  2. M 6.0 Near San Bernardino, California
    December 16, 1858 · epicentre 20 km from the trace

Before 1973 from the USGS ComCat historical catalogue (within 25 km; epicentres of old earthquakes are estimates). Since 2016, M4+ within 10 km.

Most recent near it

  1. M 2.6 7 km ENE of Big Bear City, CA
    2025-12-19 · 9 km from the trace
  2. M 2.8 3 km N of Big Bear City, CA
    2025-11-01 · 7 km from the trace
  3. M 2.6 7 km N of Big Bear City, CA
    2025-10-05 · 4 km from the trace
  4. M 2.5 7 km N of Big Bear City, CA
    2025-10-05 · 4 km from the trace
  5. M 3.5 7 km N of Big Bear City, CA
    2025-10-05 · 4 km from the trace
  6. M 3.3 7 km N of Big Bear City, CA
    2025-10-05 · 4 km from the trace

Neighbouring faults

Fault trace, slip rate and age: USGS Quaternary Fault and Fold Database (public domain), simplified for the web. Earthquakes: USGS ComCat. QuakeIndex does not forecast earthquakes; a fault's history describes the past. For early warning use ShakeAlert.