Lake sediment evidence of paleoseismicity: Timing and spatial occurrence of late- and postglacial earthquakes in Finland

Ojala, Antti E. K.; Mattila, Jussi; Hämäläinen, Jyrki; Sutinen, Raimo

doi:10.1016/j.tecto.2019.228227

Cited by 15 publications

(14 citation statements)

References 75 publications

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“…Such a high stress ratio would allow the reactivation of non‐optimally orientated thrust faults with dips of

45 °

close to the ice sheet center at the end of deglaciation. This reflects the observations of the known GIFs (e.g., Lagerbäck & Sundh, 2008; Ojala et al., 2019). The stress changes in a thrust‐faulting stress regime are also the largest beneath the ice sheet center, which coincides with the location of large‐magnitude reactivations during and after deglaciation (Arvidsson, 1996).…”

Section: Discussionsupporting

confidence: 84%

“…This is observed for the currently glaciated regions; both Greenland and Antarctica show only low seismicity, that is, a small amount of moderate earthquakes beneath the ice sheet (Lough et al., 2018; Voss et al., 2007). During deglaciation, loading‐induced stress changes are then able to reactive pre‐existing faults leading to large‐magnitude earthquakes as has been identified in the previously glaciated areas of Northern Europe (e.g., Arvidsson, 1996; Ojala et al., 2019), Greenland (R. Steffen et al., 2020), and North America (e.g., Brooks & Adams, 2020). The faults are called glacially induced faults (GIFs).…”

Section: Introductionmentioning

confidence: 95%

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Reactivation of Non‐Optimally Orientated Faults Due to Glacially Induced Stresses

Steffen

2021

Tectonics

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The deformation due to an ice load is accompanied by displacement and stress changes. These stress changes are known to have created large‐magnitude earthquakes along pre‐existing faults during and after deglaciation of the Late Quaternary ice sheets. However, these so‐called glacially induced faults have been found to be not optimally orientated in their respective regional stress regime. Here, we analyzed the potential of non‐optimally orientated fault reactivation within a glacially induced stress field as well as changes of the stress regimes due to these additional stresses. A finite element model is used to estimate glacially induced stresses, which are then combined with background stress magnitudes. Non‐optimally orientated faults can be reactivated by glacially induced stresses within thrust‐, strike‐slip‐, and normal‐faulting stress regimes, but depending on their location with respect to the ice sheet and their orientation within the regional stress field. While faults with large variations of dip and strike outside of the ice sheet are prone to reactivation when the background stress field is a normal‐ or strike‐slip‐faulting stress regime, faults within a thrust‐faulting stress regime can also be reactivated within the ice margin during and after the deglaciation. Outside the ice margin, instabilities in a thrust‐faulting stress regime develop along the intermediate principal stress axis. Stress regime changes can occur for all background stress states. Finally, we find that certain conditions in a strike‐slip‐faulting stress regime can also explain the observed glacially induced thrust faults in Northern Europe.

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“…Such a high stress ratio would allow the reactivation of non‐optimally orientated thrust faults with dips of

45 °

Section: Discussionsupporting

confidence: 84%

Section: Introductionmentioning

confidence: 95%

Reactivation of Non‐Optimally Orientated Faults Due to Glacially Induced Stresses

Steffen

2021

Tectonics

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“…These observations sometimes allow assessment of the magnitude of strong earthquakes. For example, the magnitude of the Quaternary seismic tremors was estimated as large as M = 7.0 and higher in Finland (Ojala et al, 2019). Similar characteristics of Quaternary earthquakes were evaluated in Sweden (Mörner, 1995(Mörner, , 2009Lund et al, 2017).…”

Section: Introductionmentioning

confidence: 55%

“…In contrast with highly complex glacial deposits, lacustrine sediments infilling extensive paleolacustrine basins with a flat bottom surface of the bottom layer provide a unique possibility to trace neotectonic vertical movements in a more consistent way. Moreover, the lacustrine and glaciolacustrine sediments are especially sensitive to the earthquake tremors and could be documented in outcrops and in shallow seismic profiles (Doughty et al, 2014;Jakobsson et al, 2014;Shvarev et al, 2018;Ojala et al, 2019). These observations sometimes allow assessment of the magnitude of strong earthquakes.…”

Section: Introductionmentioning

confidence: 99%

Evidence of paleoseismic activity recorded in glaciolacustrine sediments predating the Weichselian glacial maximum in East Lithuania

Satkūnas

Šliaupa

2021

Quat. res.

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Soft-sediment deformation structures (SSDS) were identified in proglacial lacustrine (glaciolacustrine) sediments dated to 25–24 ka in the Buivydžiai outcrop, situated 30 km north of Vilnius in east Lithuania. These sediments accumulated in front of the last Weichselian glaciation maximum. The SSDS originated due to sandy silt liquefaction that disrupted the decimeter-thick silty sand interlayer. A NW-SE trending Buivydžiai fault was mapped in the proximity (8 km) of the Buivydžiai outcrop. The fault is well traced by a dense drilling in the sediments of the preglacial Daumantai Formation in the basal part of the Quaternary cover and attributed to the earliest Pleistocene. Depth difference of the formation along the fault is ~5–8 m; the northern flank is relatively uplifted with respect to the southern flank. The Buivydžiai earthquake was most likely induced by formation of an elastic forebulge flexure of the Earth's crust in front of the ice sheet. The magnitude was evaluated ~M = 6.0–6.5 and was most likely of shallow hypocenter depth. Furthermore, the Bystritsa (Belarus) earthquake of magnitude M = 3.5–4.0 was registered in December 1908 to the east (12 km) of the Buivydžiai outcrop along the Buivydžiai fault, which points to recurrent seismic activity of this fault.

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“…Neotectonic deformations can be readily recognized in the Quaternary marine and lacustrine sediment successions, either as faults and folds within the stratified sediments or as secondary effects such as mass-transport deposits (MTDs, e.g., Strasser et al, 2011;Wiemer et al, 2015;Moernaut et al, 2017;Wright et al, 2019;and Ojala et al, 2019), i.e., underwater landslides. The recognition of such subsurface features in the investigated area ( Figure 9) allows insights into the long-term neotectonic activity spanning the Late Pleistocene and Holocene.…”

Section: Indicators Of Neotectonic Deformations In High-resolution Shmentioning

confidence: 99%

Active Tectonics in the Kvarner Region (External Dinarides, Croatia)—An Alternative Approach Based on Focused Geological Mapping, 3D Seismological, and Shallow Seismic Imaging Data

et al. 2020

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Active tectonics in long-lived orogenic belts usually manifests on the preexisting inherited structures. In the Kvarner region of the External Dinarides, an area with low-to-moderate seismicity related to the Adriatic microplate (Adria) northward movement, we deal with faults in predominantly carbonate rocks within tectonically complex NW-SE striking fold-and-thrust belt, which makes the identification and parametrization of the active structures challenging. Moreover, anthropogenic modifications greatly complicate access to the surface geological and geomorphological data. This paper demonstrates results of focused multidisciplinary research, from surface geological mapping and offshore shallow seismic surveys to earthquake focal mechanisms, as an active fault identification and parametrization kit, with a final goal to produce an across-methodological integrated model of the identified features in the future. Reverse, normal, and strike-slip orogen-parallel (longitudinal) to transverse faults were identified during geological mapping, but there is no clear evidence of their mutual relations and possible recent activity. The focal mechanisms calculated from the instrumental record include weak-to-moderate earthquakes and show solutions for all faulting types in the upper crust, compatible with the NE-SW oriented principal stress direction, with the stronger events favoring reverse and strike-slip faulting. The 3D spatial and temporal distribution of recent earthquake hypocenters indicate their clustering along predominantly subvertical transversal and steeply NE-dipping longitudinal planes. High-resolution shallow seismic geoacoustical survey (subbottom profiler) of the Quaternary sediments in the Rijeka Bay revealed local tectonic deformations of the stratified Late Pleistocene deposits that, along with overlaying mass-transport deposits, could imply prehistorical strong earthquake effects. Neotectonic faults onshore are tentatively recognized as highly fractured zones characterized by enhanced weathering, but there is no evidence for its recent activity. Thus, it seems that the active faults are blind and situated below the thin-skinned and highly deformed early-orogenic tectonic cover of the Adria. A strain accumulating deeper in the crust is probably irregularly redistributed near the surface along the preexisting fault network formed during the earlier phases of the Dinaric orogenesis. The results indicate a need for further multidisciplinary research that will contribute to a better seismic hazard assessment in the densely populated region that is also covered by strategic infrastructure.

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Lake sediment evidence of paleoseismicity: Timing and spatial occurrence of late- and postglacial earthquakes in Finland

Cited by 15 publications

References 75 publications

Reactivation of Non‐Optimally Orientated Faults Due to Glacially Induced Stresses

Reactivation of Non‐Optimally Orientated Faults Due to Glacially Induced Stresses

Evidence of paleoseismic activity recorded in glaciolacustrine sediments predating the Weichselian glacial maximum in East Lithuania

Active Tectonics in the Kvarner Region (External Dinarides, Croatia)—An Alternative Approach Based on Focused Geological Mapping, 3D Seismological, and Shallow Seismic Imaging Data

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