A seismic gap is a segment of an

active fault An active fault is a fault that is likely to become the source of another earthquake sometime in the future. Geologists commonly consider faults to be active if there has been movement observed or evidence of seismic activity during the last 10,0 ...

known to produce significant

earthquake An earthquakealso called a quake, tremor, or tembloris the shaking of the Earth's surface resulting from a sudden release of energy in the lithosphere that creates seismic waves. Earthquakes can range in intensity, from those so weak they ...

s that has not slipped in an unusually long time, compared with other segments along the same structure. There is a hypothesis or theory that states that over long periods, the displacement on any segment must be equal to that experienced by all the other parts of the fault. Any large and longstanding gap is, therefore, considered to be the fault segment most likely to suffer future earthquakes. The applicability of this approach has been criticised by some

seismologist Seismology (; from Ancient Greek σεισμός (''seismós'') meaning "earthquake" and -λογία (''-logía'') meaning "study of") is the scientific study of earthquakes (or generally, quakes) and the generation and propagation of elastic ...

s, although earthquakes sometimes have occurred in previously identified seismic gaps.

Examples

Loma Prieta Seismic Gap, California

Prior to the

1989 Loma Prieta earthquake On October 17, 1989, at 5:04 p.m. Pacific Time Zone, PST, the Loma Prieta earthquake occurred at the Central Coast (California), Central Coast of California. The shock was centered in The Forest of Nisene Marks State Park in Santa Cruz Cou ...

( = 6.9), that segment of the

San Andreas Fault The San Andreas Fault is a continental Fault (geology)#Strike-slip faults, right-lateral strike-slip transform fault that extends roughly through the U.S. state of California. It forms part of the tectonics, tectonic boundary between the Paci ...

system recorded much less seismic activity than other parts of the fault. The main shock and

aftershock In seismology, an aftershock is a smaller earthquake that follows a larger earthquake, in Epicenter, the same area of the Mainshock, main shock, caused as the displaced Crust (geology), crust adjusts to the effects of the main shock. Large earthq ...

s of the 1989 event occurred within the previous seismic gap.

Central Kuril gap, Russia

Immediately following the

2004 Indian Ocean earthquake On 26 December 2004, at 07:58:53 local time (UTC+07:00, UTC+7), a major earthquake with a magnitude of 9.2–9.3 struck with an epicenter, epicentre off the west coast of Aceh in northern Sumatra, Indonesia. The Submarine earthquake, undersea ...

, a seismic gap analysis of the seismic zones around the Pacific Ocean identified the Central Kuril segment of the Kuril–Kamchatka Trench

subduction Subduction is a geological process in which the oceanic lithosphere and some continental lithosphere is recycled into the Earth's mantle at the convergent boundaries between tectonic plates. Where one tectonic plate converges with a second p ...

zone as the most likely to give rise to a major earthquake. This zone, 500 km in length, at that time had experienced no major earthquake since 1780, but was bounded to north and south by segments that had moved within the last 100 years. The M_w = 8.3 earthquake of 15 November 2006 and the = 8.2 earthquake of 13 January 2007 occurred within the defined gap.

Central Himalayan Gap, India

Although there had been earthquakes to the west (near Delhi) in 1905, and to the east ( Nepal–India earthquake) in 1934, there was a 600-kilometer-long region of the central Himalayan that had not ruptured since 1505. In April 2015, the 7.8

April 2015 Nepal earthquake The April 2015 Nepal earthquake (also known as the Gorkha earthquake) killed 8,962 people and injured 21,952 across the countries of Nepal, India, China and Bangladesh. It occurred at on Saturday 25 April 2015, with a magnitude of Moment magni ...

occurred near the center of this region.

Cascadia, United States–Canada

The only known damaging earthquakes to have occurred in the Cascadia subduction zone since the 1700 Cascadia earthquake are the 1946 Vancouver Island earthquake and 2001 Nisqually earthquake.

Meiktila gap, Myanmar

On the Sagaing Fault, geologists identified a long section of the fault between Mandalay and Naypyidaw with no historical ruptures since at least 1918. They published their findings in 2011 and concluded that at least of slip had accumulated along the length of the gap. If the entire gap ruptured, the expected magnitude would be around 7.9. Another study in 2014 sugested that the seismic gap last ruptured during the 23 March 1839 earthquake. On 28 March 2025, a section of the Sagaing Fault, including the gap, ruptured in a magnitude 7.7 earthquake.

References

External links

USGS glossary entry
{{DEFAULTSORT:Seismic Gap Seismology