Mammoth Lakes Faults

Long Valley Caldera

Mammoth Lakes Area Faults:

Long Valley Caldera Fault Map

Long Valley Caldera Faults

Owens Gorge Fault Map

Owens Gorge Faults

Bishop California Fault Map

Bishop California Faults

Mono Lake Fault Map

Mono Lake Faults

Long Valley Caldera

In the early eighties a strong earthquake swarm that included four Richter magnitude 6 earthquakes hit and awoke the southern margin of Long Valley Caldera associated with a ten inch dome-formed upward movement of the huge caldera basin. These earthquakes marked the onset of the latest era of caldera seismic unrest that continues to this day. This ongoing movement includes recurring area earthquake swarms and continued dome bulge uplift of the central area of the caldera (name: resurgent dome) paired with changes in thermal springs activity and temperatures, and gas emissions. After the large May 25, 1980 earthquake another area road was created as an evacuation route. It was first named first the "Mammoth Escape Route" but was changed to the “Mammoth Scenic Loop" after Mammoth area businesses and property owners complained.
The recurring past earthquake swarms and episodes of ground uplift (particularly the uplift centered on Long Valley Caldera’s resurgent dome) that dominated the geologic unrest in Long Valley Caldera through the early 1980’s and 199’s emphasize that this large silicic magmatic system is still active and capable of producing volcanic eruptions.

The four level color code warning conditions were developed in collaboration with Mono County, the Town of Mammoth Lakes, the California Earthquake Prediction Evaluation Council (CEPEC) and the California Division of Mines and Geology (CDMG). It was formally adopted in June 1997 in an effort to simplify and clarify the five level alphabetic E through A status system initially adopted in 1991. The color code system through condition ORANGE is based on activity levels and rates for premonitory activity commonly observed prior to the onset of a volcanic eruption.

Background typically includes several Mag 2 earthquakes, day with 10-20 smaller events and C02 emissions at Mammoth Mountain < 500 t/day

A swarm and 1 Magnitude 5, 5 Magnitude 4, or 30 Magnitude 3 events; day OR Average strain rates of 1 ppm day or displacements of 5 mm day on 3 or more instruments sustained for 48 hours.

Accelerating Intense Unrest ERUPTION LIKELY within hours or days.

Eruptive activity characterized by any of the following:
Small-Large explosive blasts either phreatic or magmatic
Effusive lava fountains feeding fluid lava flows
Dome growth
Eruption column if present may reach 1 km above vent elevation
Hazardous zone(s) subject to ballistic ejecta or small pyroclastic flows generally limited to 1 to 2 km from eruption vent’s
Minor downwind ash fall possible

Long Valley Caldera Ring Fault Map Resources

USGS Significant Earthquakes Archive
Find out if your home is in a seismic liquefaction or landslide area

Long Valley Caldera

Long Valley Caldera USGS Volcano Hazards Watch

Long Valley Caldera and Mono-Inyo Craters Volcanic Field, California

Fault Attributes Key

NAME is an 80-character field for the name of the fault (including section name,
i.e., Denali fault, Holitna section). Fault and section are lower case.

CODE is a three-integer field.that defines certainty or reliability of field mapping
(integer one), time of most recent movement (integer two), and amount or rate of slip (integer three).
CODE is composite of the single integer fields ACODE, SLIPCODE, and FCODE
and determines the line type (fault trace) to be plotted.

NUM is a six-character unique USGS identifier that defines a fault or section id. Simple fault
ids are only numeric; section ids are alpha numeric.

AGE is the upper bounding time of the most recent surface-deforming earthquake. The allowable
choices are provided in a pull-down menu.

ACODE is the second integer in CODE and defines the upper bounding time of the most recent
surface-deforming earthquake.
Permissible values are between 1 and 6: 1=historic «150 years; red =cmyk 1096680);
2= post glacial (15,000 years; orange = cmyk 1 38 1000);
3 = late Quaternary «130,000 years; green> cmyk 1002500);
4 =middle and late Quaternary «750,000 years: blue > cmyk 1004440);
5 =Quaternary «1,600,000 years; black 5);
6 = Class B (black halftone)
In the text documentation, Quaternary faults (integer two, 1-5) are Class A structures. Questionable or
suspected structures are Class B (integer two, 6).

SLIPRATE is the assigned slip rate category.

SLIPCODE is the third integer in CODE and defines the assigned slip rate category. Permissible
values are between 1 and 4 and determines line width:
1=>5 mm/year (extra wide; .048):
2 =1-5 mm/year (wide; .0325):
3 =0.2-1 mm/year (medium; .025);
4 =<.2 mm/year (thin; .015)

SLIPSENSE is normal, reverse, strike slip, thrust

DIPDIRECTION is one of the eight quadrant dip directions for the entire fault or section, not the
individual arc. C = center E =east N_ =north NE =northeast NW =northwest S =south SE =southeast SW =
southwest W_ =west
SLIPDIRECT (we are not using that field anymore and can be left empty) FCODE is the first integer
in CODE and defines how well the fault is located and expressed in the landscape. Permissible values are

between 1 and 3:
1 = fault landforms are more continuous than discontinuous and mapping is accurate at
given MAPPEDSCALE (solid);
2 = fault landforms are more discontinuous than continuous and mapping is accurate at
given MAPPEDSCALE (dashed);
3 = location of fault is inferred (dotted)
FTYPE is one of three allowable choices provided in a pull-down menu: Well constrained (FCODE 1),
Moderately constrained (FCODE 2), and Inferred (FCODE 3)

MAPPEDSCALE is one of four allowable choices provided in a pull-down menu.
Mapped scale will control visualization of the fault at various scales.
1:24,000, fault should be more continuous than discontinuous and mapping is accurate at <10,000 scale.
1:50,000, fault should be more continuous than discontinuous and mapping is accurate at <25,000 scale.
1:100,000, fault could be more discontinuous than continuous and mapping is accurate at <50,000 scale.
1:250,000, fault location may be inferred or is poorly constrained.

Click on the fault lines for more information.
Note* The earthquake faults are color coded by unique name and section not type.

Data source: USGS
CCCarto is not responsible for data errors or omissions, use as reference only.

Other Earthquake Fault Maps:

Region Faults
Los Angeles Harbor Tsunami Threat

Other Web Maps:

Main Web Map Index