Magnitude and source area estimations of severe prehistoric earthquakes in the western Austrian Alps

Abstract. In slowly deforming intraplate tectonic regions such as the Alps only limited knowledge exists on occurrence of severe earthquakes, their maximum possible magnitude, and potential source areas. This is mainly due to long earthquake recurrence rates exceeding time span instrumental records historical documentation. Lacustrine paleoseismology aims at retrieving long-term continuous seismic shaking. A paleoseismic record from a single lake provides information events for which shaking exceeded intensity threshold site. addition, when positive negative evidence multiple sites can be gathered certain period, minimum magnitudes locations estimated paleo-earthquakes by reverse application an empirical prediction equation in geospatial analysis. Here, we present four western Austrian based integration available updated data, comprise mass-transport deposits reflection profiles turbidites soft-sediment deformation structures sediment cores. The Plansee Achensee covering last ∼10 kyr were extended towards age initiation after deglaciation obtain longest catalogue each Our results show that 25 earthquakes are recorded lakes Plansee, Piburgersee, Achensee, potentially Starnbergersee over ∼16 kyr, interpreted have left imprints two or more lakes. Earthquake intervals range ca. 1000 2000 years, with weakly periodic aperiodic behavior individual records. We interpret relatively shorter orogen-internal archives Piburgersee related enhanced loading, whereas longer rate orogen-external archive might reflect decreased stress transfer across current-day seismicity zone. Plausible epicenters paleo-earthquake scenarios coincide current regions. Prehistoric moment magnitude (Mw) 5.8–6.1 occurred around Inn valley, Brenner region, Fernpass–Loisach region reached up Mw 6.3 Achensee. hint shift activity near valley east west during postglacial times. ShakeMaps highlight do not solely impact Tyrol but widely affect adjacent like southern Bavaria Germany.