The 1906 Aleutian Islands earthquake occurred at 00:11 UTC on August 17. It had an estimated

seismic moment Seismic moment is a quantity used by seismologists to measure the size of an earthquake. The scalar seismic moment M_0 is defined by the equation M_0=\mu AD, where *\mu is the shear modulus of the rocks involved in the earthquake (in pascals (Pa), ...

of 3.8 x 10²⁸ dyn cm⁻¹, equivalent to a magnitude of 8.35 on the

moment magnitude scale 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 ...

. This earthquake was followed thirty minutes later by the

1906 Valparaíso earthquake The 1906 Valparaíso earthquake hit Valparaíso, Chile, on August 16 at 19:55 local time. Its epicenter was offshore from the Valparaíso Region, and its intensity was estimated at magnitude 8.2 . This earthquake occurred thirty minutes after the ...

in Chile, but the two events are not thought to be linked. Due to the remote location, there are no reports of damage associated with this earthquake. A transpacific

tsunami A tsunami ( ; from ja, 津波, lit=harbour wave, ) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater exp ...

reported from Japan and Hawaii was triggered by the Chilean event, rather than the Aleutian Islands earthquake.

Tectonic setting

The

Aleutian Islands The Aleutian Islands (; ; ale, Unangam Tanangin,”Land of the Aleuts", possibly from Chukchi ''aliat'', "island"), also called the Aleut Islands or Aleutic Islands and known before 1867 as the Catherine Archipelago, are a chain of 14 large v ...

are a

volcanic arc A volcanic arc (also known as a magmatic arc) is a belt of volcanoes formed above a subducting oceanic tectonic plate, with the belt arranged in an arc shape as seen from above. Volcanic arcs typically parallel an oceanic trench, with the arc lo ...

lying above the

convergent boundary A convergent boundary (also known as a destructive boundary) is an area on Earth where two or more lithospheric plates collide. One plate eventually slides beneath the other, a process known as subduction. The subduction zone can be defined by a ...

where the Pacific Plate is being subducted beneath the

North American Plate The North American Plate is a tectonic plate covering most of North America, Cuba, the Bahamas, extreme northeastern Asia, and parts of Iceland and the Azores. With an area of , it is the Earth's second largest tectonic plate, behind the Pacif ...

. Earthquakes in the area are caused by movement along the plate interface (such as the 1965 Rat Islands earthquake), normal faulting within the outer rise and within the subducting slab. The earthquake's

epicenter The epicenter, epicentre () or epicentrum in seismology is the point on the Earth's surface directly above a hypocenter or focus, the point where an earthquake or an underground explosion originates. Surface damage Before the instrumental pe ...

lies close to a major break in the Aleutian chain, between the

Andreanof Islands The Andreanof Islands ( ale, Niiĝuĝim tanangis, russian: Андреяновские острова) are a group of islands in the Aleutian Islands in southwestern Alaska. They are located at about 52° North and 172°57' to 179°09' West. Geogr ...

to the east and the Rat Islands to the west, along what is known as the Amchitka channel. In this region there is evidence for a tear in the lithosphere of the descending slab. It is thought that this tear is caused by the unusually sharp curvature of this part of the arc coupled with the interaction of Bowers Ridge in the over-riding plate with the subduction zone.

Earthquake characteristics

Analysis of this earthquake using modern techniques has been possible due to the large collection of seismograms recording this event published in 1907. They came from 78 stations around the world and included details of the characteristics of the individual seismometers. The focal mechanism of the earthquake has been determined from the seismograms as a normal faulting event within the subducting slab, with a large component of left-lateral

strike-slip faulting In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...

. A tsunami was recorded in both Japan and Hawaii in the hours following the earthquake. A run-up of reported from Maui was too early to be related to either of the earthquakes. Based on the estimated focal mechanism of the Aleutian Islands event and the timing of the observed run-ups, the tsunami is thought to have resulted from the earthquake in Chile.

Relationship to the 1906 Valparaíso earthquake

The short time interval between these two major earthquake has raised the possibility of the event in Chile being triggered in some way by the earlier earthquake in the Aleutian Islands, particularly as the later event occurred during the passage of the

wavefront In physics, the wavefront of a time-varying '' wave field'' is the set ( locus) of all points having the same '' phase''. The term is generally meaningful only for fields that, at each point, vary sinusoidally in time with a single temporal fr ...

s of its body waves through the epicentral area. However, this is regarded as most likely coincidental.

References

External links

* {{Earthquakes in the United States 1906 earthquakes Aleutian 1906 Aleutian Islands earthquake 1906 tsunamis August 1906 events

Tectonic setting

Earthquake characteristics

Relationship to the 1906 Valparaíso earthquake

See also

References

External links