QuakeIndex

Fault · California

Los Osos fault

63 kmlong (39 mi), as mapped
0.2–1 mm/yrhow fast it slips
< 15,000 yearssince it last broke the surface
5quakes 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 6.0 in 1830 (Near San Luis Obispo, California) — about 32,000 times the energy of an M3.0, the size people start to feel. It released about 15 kilotons of TNT.

USGS maps it as 3 sections: Irish Hills section, Lopez Reservoir section, Newsom Ridge section.

This week vs. its last ten years

Too quiet to rank: fewer than half a year's worth of weeks with any M1.5+ quake within 5 km, in ten years. A single quake here would read as "unusual", so we do not score it.

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

San Andreas faultSan Gregorio faultHosgri faultSan Juan faultLos Alamos faultPiedras Blancas blind faultSan Simeon fault M 6.0 · 1830 · Near San Luis Obispo, California
The Los Osos fault as mapped at the surface (glowing), with the other mapped faults nearby, 5 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 6.0 Near San Luis Obispo, California
    January 1, 1830 · epicentre 11 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 2.8 5 km W of Baywood-Los Osos, CA
    2024-01-01 · 2 km from the trace
  2. M 3.1 8 km NW of Avila Beach, CA
    2023-12-27 · 6 km from the trace
  3. M 2.5 3km NNW of Avila Beach, CA
    2019-03-18 · 8 km from the trace
  4. M 2.5 12 km W of Cayucos, California
    2016-05-24 · 3 km from the trace
  5. M 3.1 13 km W of Cayucos, California
    2016-05-24 · 3 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.