Three‐dimensional numerical modeling of slip rate variations on normal and thrust fault arrays during ice cap growth and melting

Abstract

[1] Changes in the volumes of ice caps considerably alter the stress state of the lithosphere by generating a transient signal that is added to the tectonic background stress field. These stress field changes, in turn, affect crustal deformation and in particular the slip behavior of existing faults. Here we use three-dimensional finite element models to investigate how arrays of normal and thrust faults near a growing and subsequently melting ice cap are influenced in their slip evolution. The results show that regardless of fault dip, both types of faults experience a decrease in their slip rate during ice cap advance and an increase in their slip rate during ice cap retreat if they are located beneath the ice cap. In contrast, faults outside the ice cap that are loaded on their footwall or hanging wall only show the opposite pattern: their slip rate increases during glacial loading and decreases during subsequent unloading. If the load is located along strike of the fault; that is, at one of its tips, the slip behavior of normal and thrust faults is different: The normal fault shows a slip rate increase during unloading, the thrust fault during loading. Our results explain the location and timing of deglaciation-induced paleoearthquakes in Scandinavia and the contrasting slip histories reported from normal faults in the Basin and Range Province, which are located at different positions relative to the former Yellowstone ice cap. More generally, our findings imply that a uniform slip behavior of faults in formerly glaciated regions should not be expected.Citation: Hampel, A., R. Hetzel, G. Maniatis, and T. Karow (2009), Three-dimensional numerical modeling of slip rate variations on normal and thrust fault arrays during ice cap growth and melting,

Evidence for the release of long‐term tectonic strain stored in continental interiors through intraplate earthquakes

“…First, consistent with previous studies [Wu et al, 1999;Lambeck and Purcell, 2003;Hampel et al, 2009;Lund et al, 2009], we find that the removal of the ice load, and hence the reduction in vertical stress at the surface, reduces the normal stress on NNE-SSWstriking thrust faults (Figure 2e-h). This 'unclamping' decreases the shear stress required to cause failure, hence triggering rupture on faults where the shear stress was already close to that required for failure.…”

Glacial isostatic adjustment in Fennoscandia—A review of data and modeling

“…Recently, finite-element models have been developed to study the slip evolution of a single fault plane embedded in a layered lithosphere (Hetzel and Hampel, 2005;Hampel and Hetzel, 2006;Turpeinen et al, 2008;Maniatis and Hampel, 2008;Hampel et al, 2009Hampel et al, , 2010a. Their results basically confirm that faults become more stable during glacial loading, but become unstable upon unloading.…”

Pulsed strain release on the Altyn Tagh fault, northwest China

“…For interpretation of the references to color in this figure, please refer to the web version of this article. Brothers et al, 2011;Hampel and Hetzel, 2006;Hampel et al, 2009;Hetzel and Hampel, 2005;Karow and Hampel, 2010;Luttrell et al, 2007;Turpeinen et al, 2008). The modern Ayakkum and Aqigekule Lakes are located ∼70 km and ∼100 km south of the central ATF (Figs.…”