Central Switzerland lies tectonically in an intraplate area and recurrence rates of strong earthquakes exceed the time span covered by historic chronicles. However, many lakes are present in the area that act as natural seismographs: their continuous, datable and high‐resolution sediment succession allows extension of the earthquake catalogue to pre‐historic times. This study reviews and compiles available data sets and results from more than 10 years of lacustrine palaeoseismological research in lakes of northern and Central Switzerland. The concept of using lacustrine mass‐movement event stratigraphy to identify palaeo‐earthquakes is showcased by presenting new data and results from Lake Zurich. The Late Glacial to Holocene mass‐movement units in this lake document a complex history of varying tectonic and environmental impacts. Results include sedimentary evidence of three major and three minor, simultaneously triggered basin‐wide lateral slope failure events interpreted as the fingerprints of palaeoseismic activity. A refined earthquake catalogue, which includes results from previous lake studies, reveals a non‐uniform temporal distribution of earthquakes in northern and Central Switzerland. A higher frequency of earthquakes in the Late Glacial and Late Holocene period documents two different phases of neotectonic activity; they are interpreted to be related to isostatic post‐glacial rebound and relatively recent (re‐)activation of seismogenic zones, respectively. Magnitudes and epicentre reconstructions for the largest identified earthquakes provide evidence for two possible earthquake sources: (i) a source area in the region of the Alpine or Sub‐Alpine Front due to release of accumulated north‐west/south‐east compressional stress related to an active basal thrust beneath the Aar massif; and (ii) a source area beneath the Alpine foreland due to reactivation of deep‐seated strike‐slip faults. Such activity has been repeatedly observed instrumentally, for example, during the most recent magnitude 4·2 and 3·5 earthquakes of February 2012, near Zug. The combined lacustrine record from northern and Central Switzerland indicates that at least one of these potential sources has been capable of producing magnitude 6·2 to 6·7 events in the past.
Paleoseismic record in lake deposits in Central Switzerland 343 ZUSAMMENFASSUNG In den bis zu 15,000 Jahre alten Sedimenten von vier Seen in der Zentralschweiz wurden Spuren von drei starken historischen und mindestens sieben prähistorischen Erdbeben gefunden. Der Schweizer Erdbebenkatalog der letzten 1000 Jahre verzeichnet in der Zentralschweiz drei grössere Erdbeben mit Magnituden zwischen Mw=5.7 und Mw = 6.2 (1964 AD Alpnach, 1774 AD Altdorf, 1601 AD Unterwalden) sowie ein katastrophales Mw = 6.9 Ereignis in Basel im Jahre 1356 AD. Zur Bestimmung der Wiederkehrraten dieser starken Erdbeben wurden mit Hilfe von hochauflösender Seismik und Sedimentkernanalysen paläoseismische Untersuchungen in vier verschiedenen Seen in der Zentralschweiz durchgeführt (Lungerer See, Baldegger See, Seelisberg Seeli und Vierwaldstätter See). In Abhängigkeit von der Geometrie des Seebeckens, des Sedimenttyps und der lokalen Bodenerschütterung treten wäh-rend eines Erdbebens grosse subaquatische Rutschungen oder kleine in-situ Deformationsstrukturen auf. Die Spuren der historischen Erdbeben zeigen, dass Seesedimente nur ab einer Magnitude von Mw>5.7 und bei einer lokalen Bodenerschütterung der Intensität >VII deformiert werden. Mindestens sechs prähistorische Erdbeben in der Zentralschweiz (Epizentrum und Magnitude ähnlich wie beim Mw=6.2 Unterwalden Erdbeben), sowie ein starkes prähisto-risches Erdbeben in der Baselregion (Magnitude ähnlich wie beim Mw = 6.9 Basel Erdbeben) konnten anhand der Art und regionalen Verteilung der Deformationsstrukturen bestimmt werden. Darüber hinaus gibt es Hinweise auf ein weiteres Ereignis in der Nähe von Basel und vier weitere Ereignisse in der Zentralschweiz. Im Vergleich zum Mittleren Holozän scheint die Erdbebenhäufigkeit in der Zentralschweiz erhöht während des Spätpleistozäns/Frühho-lozäns und während der letzten 4000 Jahre. Dies kann einerseits auf isostatische Ausgleichsbewegungen nach dem Abschmelzen des Eises vor 15,000 Jahren, sowie auf eine periodische Aktivierung einer alpinen seismogenen Zone in jüngerer Zeit zurückgeführt werden. ABSTRACTTraces of three larger historic and at least seven prehistoric earthquakes during the last 15,000 years were found in the sedimentary record of four lakes in Central Switzerland. The Swiss historic earthquake catalogue of approximately the last 1000 years reports three larger earthquakes in Central Switzerland with moment magnitudes varying between Mw = 5.7 and Mw = 6.2 (1964 AD Alpnach, 1774 AD Altdorf, 1601 AD Unterwalden) and the nearby catastrophic Mw = 6.9 event close to Basel in 1356 AD. In order to determine the recurrence intervals of such events and thus, the seismic hazard and risk, paleoseismic investigations were carried out in four different lakes of Central Switzerland (Lungerer See, Baldegger See, Seelisberg Seeli, Vierwaldstätter See) using high-resolution seismic data and sediment core analyses. Depending on lake basin geometry, sediment type and local ground shaking earthquake-induced deformation structures comprise large-scale mass...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.