Remotely triggered earthquakes
Encyclopedia
Remotely triggered earthquakes have also been characterized as "the very long reach of very large earthquakes." Fundamentally, it is postulated that large earthquake
s can have an influence outside of the immediate aftershock
zone, and actually activate other earthquakes at considerable distance . The further one gets from the initiating earthquake in both space and time, the more controversial is the association.
The physics involved in actually triggering an earthquake is complex. Most earthquake-generating zones are in a state of being close to failure. If such a zone were to be left completely alone, it would generate significant earthquakes spontaneously. Remote earthquakes, however, are in a position to disturb this critical state, either by shifting the stresses statically, or by dynamic change caused by passing seismic waves.
The first type of triggering may be due to static changes in the critical state. For example, after the magnitude 7.3 Landers earthquake
struck California in 1992, it is said that the earthquake map of California lit up like a Christmas tree. This event reinforced the idea of remotely triggered earthquakes, and pushed the hypothesis into the scientific mainstream.
One of the clearest examples of remote earthquake linkage is the westward migration of large earthquakes on the North Anatolian Fault
. A plot of historical earthquakes clearly shows this happening. It is inevitable that final earthquake of the current series will occur close to Istanbul
, although, as always, the exact timing is unknown.
There is scientific evidence for a 'long reach', mainly in the form of discrete element modelling
used in the mining industry. If rock is modeled as discrete elements in a critical state, it is amazing at how far a single disturbance can influence the mass. This happens every day, such as when a small excavation in a valley can bring down the whole mountainside (landslide
).
It becomes much more controversial as claims are made, for example, that recent seismic activity in California has been activated by an earthquake in Chile. Although there have been many such associations in the historical records, the physics is difficult to justify. This is an area where much more research is required.
Earthquake
An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...
s can have an influence outside of the immediate aftershock
Aftershock
An aftershock is a smaller earthquake that occurs after a previous large earthquake, in the same area of the main shock. If an aftershock is larger than the main shock, the aftershock is redesignated as the main shock and the original main shock is redesignated as a foreshock...
zone, and actually activate other earthquakes at considerable distance . The further one gets from the initiating earthquake in both space and time, the more controversial is the association.
The physics involved in actually triggering an earthquake is complex. Most earthquake-generating zones are in a state of being close to failure. If such a zone were to be left completely alone, it would generate significant earthquakes spontaneously. Remote earthquakes, however, are in a position to disturb this critical state, either by shifting the stresses statically, or by dynamic change caused by passing seismic waves.
1992 Landers earthquake
The 1992 Landers earthquake was a magnitude 7.3 earthquake that occurred on June 28, 1992 with an epicenter near the town of Landers, California...
struck California in 1992, it is said that the earthquake map of California lit up like a Christmas tree. This event reinforced the idea of remotely triggered earthquakes, and pushed the hypothesis into the scientific mainstream.
One of the clearest examples of remote earthquake linkage is the westward migration of large earthquakes on the North Anatolian Fault
North Anatolian Fault
The North Anatolian Fault is a major active right lateral-moving strike-slip fault in northern Anatolia which runs along the transform boundary between the Eurasian Plate and the Anatolian Plate. The fault extends westward from a junction with the East Anatolian Fault at the Karliova Triple...
. A plot of historical earthquakes clearly shows this happening. It is inevitable that final earthquake of the current series will occur close to Istanbul
Istanbul
Istanbul , historically known as Byzantium and Constantinople , is the largest city of Turkey. Istanbul metropolitan province had 13.26 million people living in it as of December, 2010, which is 18% of Turkey's population and the 3rd largest metropolitan area in Europe after London and...
, although, as always, the exact timing is unknown.
There is scientific evidence for a 'long reach', mainly in the form of discrete element modelling
Discrete element method
A discrete element method , also called a distinct element method is any of family of numerical methods for computing the motion of a large number of particles of micrometre-scale size and above...
used in the mining industry. If rock is modeled as discrete elements in a critical state, it is amazing at how far a single disturbance can influence the mass. This happens every day, such as when a small excavation in a valley can bring down the whole mountainside (landslide
Landslide
A landslide or landslip is a geological phenomenon which includes a wide range of ground movement, such as rockfalls, deep failure of slopes and shallow debris flows, which can occur in offshore, coastal and onshore environments...
).
It becomes much more controversial as claims are made, for example, that recent seismic activity in California has been activated by an earthquake in Chile. Although there have been many such associations in the historical records, the physics is difficult to justify. This is an area where much more research is required.