A Secondary Zone of Uplift Due to Megathrust Earthquakes

Abstract

The 1960 M9.5 Valdivia and 1964 M9.2 Alaska earthquakes caused a decimeters high secondary zone of uplift a few hundred kilometers landward of the trench. We analyze GPS data from the 2010 M8.8 Maule and 2011 M9.0 Tohoku-Oki earthquakes to reveal the persistent existence of a secondary zone of uplift due to great earthquakes at the megathrust interface. This uplift varies in magnitude and location, but consistently occurs at a few hundred kilometers landward from the trench and is likely mainly coseismic in nature. This secondary zone of uplift is systematically predicted by our 2D visco-elasto-plastic seismothermo-mechanical numerical simulations, which model both geodynamic and seismic cycle timescales. Through testing hypotheses in both simple and realistic setups, we propose that a superposition of two physical mechanisms could be responsible for this phenomenon. First, a wavelength is introduced through elastic buckling of a visco-elastically layered fore-arc that is horizontally compressed in the interseismic period. The consequent secondary zone of interseismic subsidence is elastically rebound during the earthquake into a secondary zone of relative uplift. Second, absolute and broader uplift is ensured through a mass conservationdriven return flow following accelerated slab penetration due to the megathrust earthquake. The dip and width of the seismogenic zone and resulting (deep) coseismic slip seem to have the largest affect on location and amplitude of the secondary zone of uplift. These results imply that subduction and mantle flow do not occur at constant rates, but are rather modulated by earthquakes. This suggests a link between deep mantle and shallow surface displacements even at time scales of minutes.

Insights Into the Sea-Level History of the South Shetland Islands From Ground Penetrating Radar on Livingston Island, Antarctica

“…Uplift zones of 15 m across an area of 965 km by 210 km were observed (Plafker, 1969) and is more than adequate to encompass the dimensions of the SSI. The megathrust tectonic regime is similar between the two regions making rapid uplift a plausible stranded beach ridge forming hypothesis (Plafker,34 1969; Barsch and Masbaucher, 1986;Taylor et al, 2008;Dinther et al, 2019). Additionally, no Holocene fault scarps have been identified within the SSI as would be expected if fault rupture during earthquakes caused uplift of the beaches to form the isolated ridges across the island chain (Simms et al, 2012).…”

Thermodynamically consistent model for poroelastic rocks towards tectonic and volcanic processes and earthquakes

“…1]. Sometimes, this corotational objective time derivative is also used in geophysical modelling, viz [2,12,19,34,38,57] or [18,Chap.12]. It allows for a proper modelling of situations when the medium rotates within rock folding or magma vortices.…”

“…8), which can be here exploited for solidification of magma and melting of rocks. Some small-strain non-convective variants have been devised damage-less in [57,58] or isothermal in [47,50].…”

Cluster Analysis of Marine Terraces and Quantitative Seismotectonic Interpretation of the Boso Peninsula, Central Japan

“…There are some possible reasons for this difference. For example, T. Sato et al (2016) assumed stratified viscoelastic structure, but a lateral heterogeneity of viscoelastic structure can significantly affect the viscoelastic response and the pattern of crustal deformation (e.g., van Dinther et al, 2019). The geometry of the plate interface also affects the deformation pattern, where more realistic and irregular plate interface can generate more irregular surface deformation.…”