Reconstructing historical seismicity from lake sediments (Lake Laffrey, Western Alps, France)

Abstract

Sediment archives from a mountain lake are used as indicators of seismotectonic activity in the Grenoble area (French western Alps, 45°N). Sedimentological analysis (texture and grain‐size characteristics) exhibits several layers resulting from instantaneous deposits in Lake Laffrey: six debris flow events up to 8 cm thick can be attributed to slope failure along the western flank of the basin. Dating with 210Pb and 137Cs gamma counting techniques and the reconnaissance of historical events, provide a constrained age‐depth model. Over the last 250 years, five of such debris flow deposits could be related to historical earthquakes of MSK intensities greater than VI over an area of <60 km. One debris flow deposit triggered at the beginning of the last century can be related to an historical landslide possibly triggered by the artificial regulation of the lake level.

Tracking Holocene glacial and high-altitude alpine environments fluctuations from minerogenic and organic markers in proglacial lake sediments (Lake Blanc Huez, Western French Alps)

“…figure 1A; Thouvenot et al, 2003;Nomade et al, 2005). Superimposed on these sedimentary processes, the occurrence of sedimentary events (SEs) rich in angular dropstones in the lacustrine sediments of LBH were as well related to the impact of frequently observed dirty snow avalanches on the lake-ice in early summer .…”

“…Lauterbach et al, 2012) and (ii) on eight chronological markers: two AMS 14 C dates on macroremains, three AMS 14 C dates on bulk sediment corrected from the occurrence of fossil organic matter, two radiocarbon dates from the nearby archaeological site correlated with Ag/Sr peaks tracking former local mining activities, and the stratigraphic correlation of SE 11 with the slump deposit from core LBH03 dated by radionuclide and related to the impact of the AD1962 Corrençon earthquake located at 47 km from LBH . This age model ( figure 6D) allows estimating the chronology of SEs (table 2) and is comforted by the correlation of SE 10 with the AD1881 Allemond earthquake (Nomade et al, 2005;Guyard et al, 2007;Wilhelm et al, 2011) located at 6 km from LBH and SE 9 either with the largest regional earthquake located next to Lake Le Bourget at 80 km from LBH in AD1822 (the Chautagne event, Chapron et al, 1999;Guyard et al, 2007), or with a smaller but local event in AD1782 (the Uriage earthquake; Nomade et al, 2005;Wilhelm et al, 2011) located at 20 km from LBH ( figure 1B) . Similarly, SE 1 is, within the age-depth models errors, synchronous, with a major subaquatic slope failure event (the HDU) in Lake Le…”

Lake Pavin Paleolimnology and Event Stratigraphy

“…This earthquake reached an MSK intensity of 4.5 at the epicenter (Sisfrance database, BRGM, Lambert 1997 ). Compared to other studies documenting the impact of historical earthquakes on lacustrine sediments from European regions characterized by a moderate seismicity (Chapron et al 1999 ;Monecke et al 2004 ;Nomade et al 2005 ;Strasser and Anselmetti 2008 ), it seems that Lake Pavin organic rich sedimentation in littoral areas is unstable and easily remobilized when submitted to gravity accelerations associated with seismic waves propagation. Following the conclusions of Strasser and Anselmetti ( 2008 ) it is, however, also very likely that this limited remobilization of littoral sediments down to PAV08 coring site has been favored by the perturbation of subaqueous sediment pore pressure after the artifi cial lake level drop by ca.…”

“…23.13 ; Table 23.2 ). According to former studies on lacustrine sediments sensitivities to instrumental earthquakes (Monecke et al 2004 ;Nomade et al 2005 ) both of these historical earthquakes could be recorded in nearby Lake Pavin. Another similar study combining radiocarbon dated sediment cores from nearby Lake Guéry (Chassiot et al 2016 ) also identifi ed a pluri-decimetric slump deposit along its delta that is contemporaneous with the AD 1863 Mont-Dore earthquake (Fig.…”

Consecutive earthquakes temporarily restructured the zooplankton community in an Alpine Lake

“…They trigger landslides and erosion, temporarily increasing water turbidity (Korup et al, 2004). On land, they can locally result in tilted and damaged trees (Carrara and O'Neill, 2003), while in lakes they can induce mud flows of considerable thickness (Nomade et al, 2005).…”