Migration of seismic and volcanic activity as display of wave geodynamic process

Abstract

Publications about the earthquake foci migration have been reviewed. An important result of such studies is establishment of wave nature of seismic activity migration that is manifested by two types of rotational waves; such waves are responsible for interaction between earthquakes foci and propagate with different velocities. Waves determining long-range interaction of earthquake foci are classified as Type 1; their limiting velocities range from 1 to 10 cm/s. Waves determining short-range interaction of foreshocks and aftershocks of individual earthquakes are classified as Type 2; their velocities range from 1 to 10 km/s. According to the classification described in [Bykov, 2005], these two types of migration waves correspond to slow and fast tectonic waves. The most complete data on earthquakes (for a period over 4.1 million of years) and volcanic eruptions (for 12 thousand years) of the planet are consolidated in a unified systematic format and analyzed by methods developed by the authors. For the Pacific margin, Alpine-Himalayan belt and the Mid-Atlantic Ridge, which are the three most active zones of the Earth, new patterns of spatial and temporal distribution of seismic and volcanic activity are revealed; they correspond to Type 1 of rotational waves. The wave nature of the migration of seismic and volcanic activity is confirmed. A new approach to solving problems of geodynamics is proposed with application of the data on migration of seismic and volcanic activity, which are consolidated in this study, in combination with data on velocities of movement of tectonic plate boundaries. This approach is based on the concept of integration of seismic, volcanic and tectonic processes that develop in the block geomedium and interact with each other through rotating waves with a symmetric stress tensor. The data obtained in this study give grounds to suggest that a geodynamic value, that is mechanically analogous to an impulse, remains constant in such interactions. It is thus shown that the process of wave migration of geodynamic activity should be described by models with strongly nonlinear equations of motion.Key words: migration, waves, rotation, seismicity, volcanism, geodynamics, conservation law, rheidity. MIGRATION OF SEISMIC AND VOLCANIC ACTIVITY AS DISPLAY OF WAVE GEODYNAMIC PROCESS

Wave moment geodynamics

“…In seismology, such interaction is well-known and evidenced by the migration of earthquake sources along seismic belts for long distances amounting to dozens of thousand kilometres [Vikulin et al, 2012a[Vikulin et al, , 2012b, as well as by remote fore-and aftershocks [Prozorov, 1978] and coupled earthquakes (p. 119-123 in [Vikulin, 2011]). …”

“…Nonetheless, the detailed analysis of migration velocities in geodynamic settings of all active zones of the Earth [Vikulin et al, 2012a] shows that this is not exactly the case. The model estimates of velocities of earthquake sources migration along the faults in Central Asia do not contradict with similar plots constructed for the Pacific margin and the Alpine-Hymalayan belt (i.e.…”

“…-An original geodynamic model is developed to show how rift basins in Pribaikalie and Transbaikalie develop in space and time [Lunina et al, 2009]; -A seismic zone is modelled in terms of tectonophysics [Sherman, 2009]; the model shows that sources of rare strong earthquakes are clustered in linear or arcshaped systems [Sherman, 2013] and migration velocities of earthquakes К≥12 (М≥4-5) range from 1 to 100 km per year [Sherman, 2013;Sherman, Gorbunova, 2008]; according to [Vikulin et al, 2012a[Vikulin et al, , 2012b, these values do not contradict with the relevant global data; -According to above-mentioned model, faults are activated by slow strain waves of excitation which are generated by interplate and interblock movements of the lithosphere [Sherman, Gorbunova, 2008] and can also occur in zones wherein seismicity is slowly migrating [Sherman, 2009[Sherman, , 2013Sherman et al, 2011]; a general assumption is that L≥l, wherein L is strain wave length and l is length of a fault activated by strain waves [Sherman et al, 2008]; -It is revealed that two major fault zones in the Baikal rift zone and the Amur River region are related; active faults are identified in both regions; it is established that the fault activation is manifested by seismicity and caused by trigger mechanisms with the leading role of slow strain waves [Sherman, 2013;Sherman et al, 2011].…”

“…A more general approach can facilitate finding original pathways to reviewing and solving geodynamic problems in the Earth sciences [Vikulin et al, 2012a[Vikulin et al, , 2012b.…”

The seismicity migration study based on space-time diagrams

“…Earthquake migration, that was first recognized in the middle of the 20th century, has been revealed in all the seismic belts of the Earth [Mogi, 1968;Ruzhich et al, 1989;Ruzhich, Levina, 2012;Vikulin et al, 2000;Chery et al, 2001;Bykov, 2005;Liu et al, 2010;Levina, Ruzhich, 2010;Levina, 2011;Vikulin et al, 2012;Sherman, 2013Sherman, , 2014Novopashina, 2013;Novopashnina, San'kov, 2015;Dolgaya, Vikulin, 2015]. The term of 'earthquake migration', however, has not been unanimously accepted due to the fact that earthquake foci and epicentres do not actually migrate but occur in the inter-block medium and are manifested in implicit patterns and trends in space and time.…”