seismology Seismology (; from Ancient Greek σεισμός (''seismós'') meaning "earthquake" and -λογία (''-logía'') meaning "study of") is the scientific study of earthquakes and the propagation of elastic waves through the Earth or through other ...

, surface rupture (or ground rupture, or ground displacement) is the visible offset of the ground surface when an

earthquake rupture In seismology, an earthquake rupture is the extent of slip that occurs during an earthquake in the Earth's crust. Earthquakes occur for many reasons that include: landslides, movement of magma in a volcano, the formation of a new fault, or, mos ...

along a fault affects the Earth's surface. Surface rupture is opposed by buried rupture, where there is no displacement at ground level. This is a major risk to any structure that is built across a fault zone that may be

active Active may refer to: Music * ''Active'' (album), a 1992 album by Casiopea * Active Records, a record label Ships * ''Active'' (ship), several commercial ships by that name * HMS ''Active'', the name of various ships of the British Royal ...

, in addition to any risk from ground shaking. Surface rupture entails vertical or horizontal movement, on either side of a ruptured fault. Surface rupture can affect large areas of land. __TOC__

Lack of surface rupture

Running track after 1999 Chichi earthquake in Taiwan

Not every earthquake results in surface rupture, particularly for smaller and deeper earthquakes. In some cases, however, the lack of surface effects is because the fault that moved does not reach the surface. For example, the

1994 Northridge earthquake The 1994 Northridge earthquake was a moment 6.7 (), blind thrust earthquake that occurred on January 17, 1994, at 4:30:55 a.m. PST in the San Fernando Valley region of the City of Los Angeles. The quake had a duration of approximately ...

had a

moment magnitude The moment magnitude scale (MMS; denoted explicitly with or Mw, and generally implied with use of a single M for magnitude) is a measure of an earthquake's magnitude ("size" or strength) based on its seismic moment. It was defined in a 1979 pape ...

of 6.7, caused major damage in the

Los Angeles Los Angeles ( ; es, Los Ángeles, link=no , ), often referred to by its initials L.A., is the largest city in the state of California and the second most populous city in the United States after New York City, as well as one of the world' ...

area, occurred at below the Earth's surface, but did not cause surface rupture, because it was a

blind thrust earthquake A blind thrust earthquake occurs along a thrust fault that does not show signs on the Earth's surface, hence the designation "blind". Such faults, being invisible at the surface, have not been mapped by standard surface geological mapping. Sometim ...

Where surface rupture occurs

Surface ruptures commonly occur on pre-existing faults. Only rarely are earthquakes (and surface ruptures) associated with faulting on entirely new fault structures. There is shallow hypocenter, and large fracture energy on the

asperities In materials science, asperity, defined as "unevenness of surface, roughness, ruggedness" (from the Latin ''asper''—"rough"), has implications (for example) in physics and seismology. Smooth surfaces, even those polished to a mirror finish, a ...

, the asperity shallower than . Examples of such earthquakes are

San Fernando earthquake The 1971 San Fernando earthquake (also known as the 1971 Sylmar earthquake) occurred in the early morning of February 9 in the foothills of the San Gabriel Mountains in southern California. The unanticipated thrust earthquake had a magnitude o ...

Tabas earthquake The 1978 Tabas earthquake occurred on September 16 at 19:05:55 local time in central Iran. The shock measured 7.4 on the moment magnitude scale and had a maximum Mercalli intensity of IX+ (''Violent''). The death toll was in the range of 15,000� ...

, and

Chi-Chi earthquake The Chi-Chi earthquake (later also known as the Jiji earthquake) (), also known as the great earthquake of September 21 (), was a 7.3 ML or 7.7 Mw earthquake which occurred in Jiji (Chi-Chi), Nantou County, Taiwan on Tuesday, 21 S ...

. In surface rupture earthquakes, the large slips of land are concentrated in the shallow parts of the fault. And, notably, permanent ground displacements which are measureable can be produced by shallow earthquakes, of

magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...

M5 and greater.

Types of surface rupture

The form that surface rupturing takes depends on two things: the nature of the material at the surface and the type of fault movement. Earthquake- road crack

Effect of surface lithology

Where there are thick superficial deposits overlying the trace of the faults, the resulting surface effects are typically more discontinuous. Where there is little or no superficial deposits, the surface rupture is generally continuous, except where the earthquake rupture affects more than one fault, which can lead to complex patterns of surface faulting, such as in the

1992 Landers earthquake The 1992 Landers earthquake occurred on Sunday, June 28 with an epicenter near the town of Landers, California, Landers, California, in San Bernardino County. The shock had a Moment magnitude scale, moment magnitude of 7.3 and a maximum Mercalli ...

Normal faulting

Surface ruptures associated with normal faults are typically simple

fault scarp A fault scarp is a small step or offset on the ground surface where one side of a fault has moved vertically with respect to the other. It is the topographic expression of faulting attributed to the displacement of the land surface by movement al ...

s. Where there are significant superficial deposits, sections with more oblique faulting may form sets of en-echelon scarp segments. Antithetic faults may also develop, giving rise to surface grabens.

Reverse faulting

Reverse faulting (particularly thrust faulting) is associated with more complex surface rupture patterns since the protruding unsupported part of the hanging-wall of the fault is liable to collapse. In addition there may be surface folding and back-thrust development.

Strike-slip faulting

Strike-slip faults are associated with dominantly horizontal movement, leading to relatively simple linear zones of surface rupture where the fault is a simple planar structure. However, many strike-slip faults are formed of overlapping segments, leading to complex zones of normal or reverse faulting depending on the nature of the overlap. Additionally, where there are thick superficial deposits, the rupture typically appears as a set of en-echelon faults.

Mitigation

To retrofit a house to survive surface rupture requires engineered design by geotechnical, and structural or civil engineers. This can be quite expensive.

Examples, with their extent

1983 Borah Peak earthquake The 1983 Borah Peak earthquake occurred on October 28, at in the western United States, in the Lost River Range at Borah Peak in central Idaho. The shock measured 6.9 on the moment magnitude scale and had a maximum Mercalli intensity of IX (''Vi ...

M6.9 in Idaho, normal faulting - *

M7.3 in San Bernardino County, California, strike-slip faulting - , *

1999 İzmit earthquake On the 17th of August, 1999 at 3:01 AM local time, a catastrophic magnitude 7.6 earthquake struck the Kocaeli Province of Turkey, causing monumental damage and 17,127–18,373 deaths. Named for the quakes proximity to the northeastern city of Izm ...

M7.6 in Turkey, strike-slip faulting - , * 1999 Jiji earthquake M7.6 in Taiwan, thrust faulting - * 2001 Kunlun earthquake M7.8 in Tibet, strike-slip faulting - * 2002 Denali earthquake M7.9 in Alaska, strike-slip faulting - * 2008 Sichuan earthquake M7.9 in Sichuan, Thrust faulting -

References

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External links and references

A large article about surface rupture
Earthquake and seismic risk mitigation Seismology Geological hazards