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The earthquake that occured on 5 February 1663 is the first strong historical earthquake recorded in Canada and is currently estimated to have been located near La Malbaie and to have had a magnitude M of about 7. It left various signatures in the landscape that reveal its extent and significance. In the terrestrial domain, landslides were observed in various regions of Quebec, including Betsiamites, Saguenay, Charlevoix, and Mauricie. In the subaqueous domain, related mass movements were found along the St. Lawrence Estuary, the Saguenay Fjord, and various lakes on the Canadian Shield and likely also in the Appalachian. The minimum cumulative volume of mass movements associated with the 1663 earthquake is 1.7 km3. From the analysis of landslide-related data and using empirical methods for magnitude estimation, the position of the epicentre would be located in the Canadian Shield to the north of the St. Lawrence River with a minimum magnitude M of 7.2 ± 0.2 and a maximum magnitude that would be close to the maximum for the Charlevoix area, which has been previously estimated at M = 7.8 ± 0.6. [ABSTRACT FROM AUTHOR]

Abstract: At least three major landslide events formed the submarine and subaerial Betsiamites (Québec, Canada) landslide complex and mobilized an estimated total volume of 2000million m3 (2km3). Linkage between offshore and onshore geophysical investigations with borehole data and in situ testing allows reconstruction of the architecture of the Betsiamites River delta area and leads to the identification of the main failure events. The submarine scar of the Betsiamites landslide complex may have resulted from a first failure, dated at about 9250cal BP, which mobilized a minimum volume of 200million m3. A second landslide dated at 7250cal BP mobilized a volume of 1300million m3 over an area of 54km2. The Betsiamites submarine landslide event dated at 7250cal BP left the largest scar yet identified on the St. Lawrence estuary seafloor. Furthermore, this paper demonstrates that the subaerial scar of the Betsiamites landslide complex is a result of the Colombier landslide event, which was initiated by the 1663 earthquake and involved four successive failure phases: one submarine and three subaerial. The February 5th 1663 earthquake triggered a submarine landslide event, which reached the shoreline, and led in a short period of time successively to two subaerial flowslides in sensitive clayey material and a subaerial lateral spread. The four failure phases mobilized a possible total volume of about 530million m3 over an area of 20km2. The Colombier landslide event is among the largest documented historic landslides in Canada. The presence of submarine scars left by the early Holocene events acted as predisposition factors for the development of the failure while the earthquake of 1663 was the main triggering factor of the first submarine failure. [Copyright &y& Elsevier]

Abstract: A complex submarine geomorphology was revealed from multibeam bathymetry and seismic reflection surveys conducted between 2001 and 2007 in the Lower St. Lawrence Estuary offshore Betsiamites River, Quebec, Canada. In this paper, we describe the submarine morpho-sedimentology of an area of ∼500 km2 with focus on the consequences of four mass movement events. The general morpho-sedimentology of the area and submarine features resulting from mass movement processes, channel erosion and gas seepage are described. A spatio-temporal sequence for the occurrence of the mass movements and a chronology for the failures are established. We propose dates for four of the observed mass movement deposits. A buried paraglacial debris flow deposit is dated as older than 9280 cal BP, whereas a major landslide scar characterized by two topographic depressions on the shelf and a sediment lobe in the Laurentian Channel were dated around 7250 cal BP. Morphological observations and sediment core analyses allow us to identify a least two different recent (i.e., less than 500 yr old) debris flow accumulations associated with two recent earthquakes: (1) the AD 1663 (M∼7) and (2) AD 1860 (M∼6) or AD 1870 (M∼6.5) earthquakes. In addition to a complex geomorphology influenced by mass movements, we have identified several regions on the shelf and on the Laurentian Channel with evidence of pockmarks, which could potentially influence submarine slope stability in the Estuary. [Copyright &y& Elsevier]

Using some new and previously published sedimentation rate data the relationship between sedimentation rate and distance from sediment source was statistically modelled for the Saguenay Fjord, Canada. Sedimentation rates obtained from these models can be used to reasonably predict the range of ages for submarine mass movements in the Saguenay Fjord. Error in the prediction is mostly associated with the natural variability of sedimentation rate. Ranges of dates were predicted for several submarine mass movements in the Upper Saguenay Fjord. In many cases the predicted date range did not correspond to the 1663 earthquake which had been previously assumed to have triggered these mass movements. [ABSTRACT FROM AUTHOR]

Analysis of morphology, failure and post-failure stages of the Palos Verdes debris avalanche reveals that it may have triggered a significant tsunami wave. Our analysis of the failure itself indicates that the slope is stable under aseismic conditions but that a major earthquake (with a magnitude around 7) could have triggered the slide. A post-failure analysis, considering the debris avalanche as a bi-linear flow, shows that peak velocities of up to 45 m/s could have been reached and that the initial movement involved a mass of rock less than 10 km wide, 1 km long and about 50–80 m thick. Initial wave height estimates vary from 10 to 50 m. Tsunami waves propagating to the local shoreline would be significantly smaller. Such a range demonstrates our lack of proper knowledge of the transition from failure to post-failure behavior related to mass movements. Further investigations and analyses of terrestrial and submarine evidence are required for a proper hazard assessment related to tsunami generation in the Los Angeles area. [Copyright &y& Elsevier]

Abstract: High-resolution seismic profiles along with physical and sedimentological properties of sediment cores from the Saguenay (Eastern Canada) and Reloncavi (Chile) Fjords allowed the identification of several decimeter to meter-thick turbidites. In both fjords, the turbidites were associated with large magnitude historic and pre-historic earthquakes including the 1663AD (M>7) earthquake in the Saguenay Fjord, and the 1960 (M 9.5), 1837 (M~8) and 1575AD major Chilean subduction earthquakes in the Reloncavi Fjord. In addition, a sand layer with exoscopic characteristics typical of a tsunami deposit was observed immediately above the turbidite associated with the 1575AD earthquake in the Reloncavi Fjord and supports both the chronology and the large magnitude of that historic earthquake. In the Saguenay Fjord, the earthquake-triggered turbidites are sometimes underlying a hyperpycnite associated with the rapid breaching and draining of a natural dam formed by earthquake-triggered landslides. Similar hyperpycnal floods were also recorded in historical and continental geological archives for the 1960 and 1575AD Chilean subduction earthquakes, highlighting the risk of such flood events several weeks or months after main earthquake. In both fjords, as well as in other recently recognized earthquake-triggered turbidites, the decimeter-to meter-thick normally-graded turbidites are characterized by a homogeneous, but slightly fining upward tail. Finally, this paper also emphasizes the sensitivity of fjords to record historic and pre-historic seismicity. [Copyright &y& Elsevier]