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It is what every geologist lives for and every paleoseismologists dreams about.

Earthquakes are caused by a sudden movement of rocks along a fault plane. The movement or displacement is called the "Fault Rupture".

The rupture begins at some depth called the focus or hypocenter. The rupture then spreads outward in all directions along the fault plane.

When the fault rupture progresses upward and reaches the Earth's surface, it creates surface fault ruptures. Yea Baby!

This is what this section is all about.

Surface fault ruptures come in all shapes and sizes but do not occur with every earthquake. They only happen when the quake is of sufficient size and is shallow enough whereby the fault rupture can break the surface.

The lowest magnitude earthquake to create surface fault ruptures is about a mid to upper M5 event. The focal depth must be shallow and on the order of less than 10 km and more like 2-6 km.

Many large, shallow earthquakes occur in the oceans but for us to see them, they must also occur on land.

Generally speaking, the larger the earthquake, the larger the potential surface fault rupture. Shallow earthquakes registering about M6.0 produce surface fault ruptures on the order of 2 feet and quakes of M8.0 generate ruptures on the order of 30-50 feet. It is extremely rare when the maximum surface fault ruptures exceed 50 ft.

Each earthquake has its own specific characteristics which govern its rupture behavior. Whether horizontal or vertical, or a combination of both, surface fault ruptures are spectacular.

This is our passion and we hope we can inspire you to join us in search of the...

Landers M7.3 earthquake, Southern California, June 28, 1992 (coming soon!)

Lavic Lake (Hector Mine) M7.1 earthquake, Southern California, October 16, 1999 <

Portola (Mohawk Valley) M5.5 earthquake, August 10, 2001 (see Special Earthquake Report while we finish the scanning of the photos.)

More shall be added shortly...

Definitions

Paleoseismology:

    paleo: old; prehistoric; ancient.
    seismology: the scientific study of the causes, effects, and characteristics of earthquakes.

  1. the study of prehistoric earthquakes.
  2. the study of past earthquakes on a fault, as determined by looking at the layers of earth and rock beneath the surface and how they have been shifted by earthquakes in the past.

Excellent reading:

Paleoseismology, 1996, edited by James P. McCalpin, Academic Press

The Geology of Earthquakes, 1997, by Robert Yeats, Kerry Sieh, and Clarence Allen, Oxford University Press.

Paleoseismology: Understanding Past Earthquakes Using Quaternary Geology, Sept-Dec 1997, edited by P.L. Hancock and A.M. Michetti, Special issue of the Journal of Geodynamics, vol. 24, nos. 1-4, 304 p.

Living with Earthquakes in the Pacific Northwest, 1998, by Robert Yeats, Oregon State University Press.

Links:

November 3, 2002
An earthquake measuring
M7.9 occurred on 11/03/02 along the east-central portion of the Alaska Range at a shallow depth of 10 km. Preliminary reports indicate large "cracks" have occurred across the ground and the Trans-Alaskan Highway near Mt. McKinley National Park. Further investigations are necessary before they can be verified as fault related.

October 10, 2002
An earthquake registering
M7.6 occurred on 10/10/02 along the northern coast of Irian Jaya, PNG, Indonesia, at the Bay of Manokwari. Preliminary data indicates the focus was shallow, about 10 km beneath the surface, suggesting the possibility of surface fault ruptures. Reuters has reported that a 3 km-long crack occurred in the Ransiki area. If tectonic in origin, this would be the first confirmed surface fault rupture since the Kunlun, China M 7.9 earthquake last November. Stay tuned for more information as it is known. Update: The focal depth was later calculated at 36 km, indicating no surface fault ruptures are expected.

March 26, 2002
An earthquake measuring
M6.0 occurred in the Hindu Kush region of Northeastern Afghanistan on 03/26/02 (see report). Preliminary data indicates the focus was shallow, about 4 km beneath the surface, suggesting the possibility of surface fault ruptures. Photos from the area show small (0.1-1.0 cm) surface cracks, however, these may be due to soil settlement rather than fault ruptures.

11/14/01 Kunlun, China M7.9 earthquake. Substantial surface fault ruptures have been discovered. Early reports suggest that maximum horizontal offsets could be as much as 7 m (22 feet) and ruptures could extend for as much as 250 km (155 mi.) See more...

The India M7.7 quake on 1/26/01. These were secondary fault ruptures, not primary. Still..

The Sept./Oct. 2001 issue of the Seismological Research Letters (SRL) has a spectacular cover photograph of the Lavic Lake (Hector Mine) surface fault ruptures.

Do you have fault rupture photos or photo sets and would like to contribute them? .

Mars Photos Show Lively Landscape - Space.com Wednesday, Nov. 7, 2001

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