Global pattern of earthquakes and seismic energy distributions: Insights for the mechanisms of plate tectonics

• Published in: Tectonophysics 2012-03, Vol.530-531, p.80-86
• Main Authors: Varga, P., Krumm, F., Riguzzi, F., Doglioni, C., Süle, B., Wang, K., Panza, G.F.
• Format: Article
• Language: English
• Subjects: Budgeting; Declustered catalogue; Dissipation; Earth; Earthquake energy distribution; Earthquakes; Energy distribution; Global seismicity; Plate tectonics; Seismic energy; Seismic engineering; Seismic phenomena
• ISSN: 0040-1951; 1879-3266
• DOI: 10.1016/j.tecto.2011.10.014

In this paper, we analyse the distributions of number of events (N) and seismic energy (E) on the Earth's surface and along its radius as obtained from the global declustered catalogue of large independent events (M≥7.0), dissipating about 95% of the Earth's elastic budget. The latitude distribution of the seismic event density is almost symmetric with respect to the equator and the seismic energy flux distribution is bimodal; both have their medians near the equator so that they are equally distributed in the two hemispheres. This symmetry with respect to the equator suggests that the Earth's rotational dynamics contributes to modulate the long-term tectonic processes. The distributions of number and energy of earthquakes versus depth are not uniform as well: 76% of the total earthquakes dissipates about 60% of the total energy in the first ~50km; only 6% of events dissipates about 20% of the total amount of energy in a narrow depth interval, at the lower boundary of the upper mantle (550–680km). Therefore, only the remaining 20% of energy is released along most of the depth extent of subduction zones (50–550km). Since the energetic release along slabs is a minor fraction of the total seismic budget, the role of the slab pull appears as ancillary, if any, in driving plate tectonics. Moreover the concentration of seismic release in the not yet subducted lithosphere suggests that the force moving the plates acts on the uppermost lithosphere and contemporaneously all over the Earth's outer shell, again supporting a rotational/tidal modulation. ► The Earth’s surface and depth distributions of large independent earthquakes M≥7.0 (N) and seismic energy (E) are analyzed. ► Latitude distributions of N and E have medians near the equator, being almost equally distributed in the two hemispheres. ► More than 60% of the energy is delivered in the shallow part of the lithosphere. ► Only 6% of events dissipates about 20% of the energy in a narrow depth interval at the lower boundary of the upper mantle. ► These data support a contribution of the Earth's rotational dynamics in driving plate tectonics.