Paraglacial rock-slope stability

https://lup.lub.lu.se/search/ws/files/3613933/3912019.pdf

Planning for climate change in urban areas : from theory to practice

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

Large earthquakes within stable continental regions (SCR) show that significant amounts of elastic strain can be released on geological structures far from plate boundary faults, where the vast majority of the Earth's seismic activity takes place. SCR earthquakes show spatial and temporal patterns that differ from those at plate boundaries and occur in regions where tectonic loading rates are negligible. However, in the absence of a more appropriate model, they are traditionally viewed as analogous to their plate boundary counterparts, occuring when the accrual of tectonic stress localized at long-lived active faults reaches failure threshold. Here we argue that SCR earthquakes are better explained by transient perturbations of local stress or fault strength that release elastic energy from a pre-stressed lithosphere. As a result, SCR earthquakes can occur in regions with no previous seismicity and no surface evidence for strain accumulation. They need not repeat, since the tectonic loading rate is close to zero. Therefore, concepts of recurrence time or fault slip rate do not apply. As a consequence, seismic hazard in SCRs is likely more spatially distributed than indicated by paleoearthquakes, current seismicity, or geodetic strain rates.

/pdf/a-new-paradigm-for-large-earthquakes-in-stable-continental-57hjym64fd.pdf

A new paradigm for large earthquakes in stable continental plate interiors

Earthquake rupture is influenced by stress conditions in the crust before the quake. Analysis and modelling of surface deformation caused by the May 2011 earthquake in Lorca, Spain, indicate that groundwater extraction influenced the pattern of fault rupture.

/pdf/the-2011-lorca-earthquake-slip-distribution-controlled-by-5gq5z8y1av.pdf

The 2011 Lorca earthquake slip distribution controlled by groundwater crustal unloading

Effect of ice sheet growth and melting on the slip evolution of thrust faults

[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

/pdf/three-dimensional-numerical-modeling-of-slip-rate-variations-35pz6odx20.pdf

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

Late Pleistocene regression of two large pluvial lakes—Lake Bonneville and Lake Lahontan—caused considerable lithospheric rebound in the Basin-and-Range Province, USA. Here, we use finite-element models to show how lake growth and regression affect the temporal and spatial slip evolution on faults near the former lakes. Our results show that fluctuations in the volume of Lake Bonneville caused along-strike slip variations on the Wasatch normal fault, with a pronounced slip rate increase on its northern and central parts during lake regression. The response of normal and strike-slip faults near the ring-shaped Lake Lahontan depends on their location within the rebound area. Faults located in the centre of rebound show a slip rate increase during lake regression, whereas strike-slip faults at the periphery decelerate. All slip rate variations are caused by differential stress changes owing to changing lake levels, regardless of the individual fault response.

Slip rate variations on faults in the Basin-and-Range Province caused by regression of Late Pleistocene Lake Bonneville and Lake Lahontan

Many active faults in extensional and contractional tectonic settings experienced a slip rate increase after the last glacial period when the volume of nearby glaciers and lakes decreased. This post-glacial slip rate increase is caused by transient stresses that are generated by the unloading-induced rebound and superimposed on the tectonic background stress field. As the latter is different for normal and thrust faults, the response to loading and unloading should depend on the fault type. Here we use finite-element models including a fault in rheologically layered lithosphere to explore the conditions under which both normal and thrust faults experience a post-glacial slip rate increase. The results show that a post-glacial slip rate increase occurs on normal faults if the lower crust is stronger than the lithospheric mantle, whereas thrust faults accelerate if the lower crust is weaker than the lithospheric mantle. These findings imply that the response of faults to mass fluctuations on the Earth9s surface may provide constraints on the rheological stratification of the lithosphere. We use our results to make predictions on the viscosity structure of the Basin-and-Range Province and northern Scandinavia, where palaeoseismological data document a pronounced increase in seismicity as a result of post-glacial unloading and rebound.

Tobias Karow

Papers

Effect of ice sheet growth and melting on the slip evolution of thrust faults

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

Slip rate variations on faults in the Basin-and-Range Province caused by regression of Late Pleistocene Lake Bonneville and Lake Lahontan

Slip rate variations on faults during glacial loading and post-glacial unloading: implications for the viscosity structure of the lithosphere