An international group of geologists have found the cause of the so-called slow earthquakes, which can last for several weeks.
Seismologists from the Paris geophysical Institute and the Massachusetts Institute of technology together with scientists of Institute of Volcanology and seismology Feb RAS found out the reason the so-called slow earthquakes, which usually last for several days or weeks, do not bring destruction, but sometimes be a harbinger of dangerous earthquakes.
The results were published in the journal Science Advances.
Theoretical works tend to indicate that the cause of the slow earthquakes is the sliding mode of lithospheric plates relative to each other. Slide areas are located at great depths, where the temperature is high enough to ensure that the breed acquired plasticity, had a little roughness and dumped the seismic tension gradually. This process is the cause of the periodicity of slow earthquakes.
To confirm the relationship of earthquakes and slow-slip portions of the crust, sandwiched between the plates, seismologists have analyzed about 1120 earthquake sources and more than 1.8 million individual cases of low-frequency seismic activity that occurred for two years in the Mexican state of Guerrero. In this area lithospheric plate Cocos dives under the North American plate.
In this area there are two phases: transient and Seating area. The movement of rocks in the area is hindered by friction, and only occurs during slippage of the plates. Soft zone is located 40 kilometers from the transient and is the source of the constant jarring of the rocks. Scientists have discovered that most cases of weak seismic activity — 955 — occurred in it. Statistical analysis showed that slow earthquakes associated with slow slip.
Transient area also was a source of oscillations with a typical magnitude that occur in the peak moment of slow earthquakes in a soft zone. Scientists emphasize that the reason for slow earthquakes, according to their study, is not a separate part of the plate subduction zone, but the interaction between different types of roughness of the rocks and the condition of the boundaries of lithospheric plates.
