QuakeIndex

Fault · California

Piedras Blancas blind fault

21 kmlong (13 mi), as mapped
0.2–1 mm/yrhow fast it slips
< 15,000 yearssince it last broke the surface
3quakes 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 6.2 in 1952 (28km NW of Cambria, CA) — about 63,000 times the energy of an M3.0, the size people start to feel. It released about 30 kilotons of TNT.

A blind thrust does not reach the surface; the line on the map is the USGS's projection of it, not a crack you can stand on.

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 faultGreat Valley thrust fault systemSan Gregorio faultHosgri faultLos Osos faultPfeiffer Point faultSan Simeon fault M 6.2 · 1952 · 28km NW of Cambria, CA
The Piedras Blancas blind fault as mapped at the surface (glowing), with the other mapped faults nearby, 3 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 6.2 28km NW of Cambria, CA
    November 22, 1952 · 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 2.6 29km WSW of San Simeon, CA
    2020-11-04 · 7 km from the trace
  2. M 2.7 22km SSW of San Simeon, CA
    2018-11-17 · 5 km from the trace
  3. M 2.6 4 km S of San Simeon, California
    2016-10-21 · 7 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.