Understanding the long-term earthquake recurrence pattern at subduction zones requires continuous paleoseismic records with excellent temporal and spatial resolution and stable threshold conditions. South central Chilean lakes are typically characterized by laminated sediments providing a quasi-annual resolution. Our sedimentary data show that lacustrine turbidite sequences accurately reflect the historical record of large interplate earthquakes (among others the 2010 and 1960 events). Furthermore, we found that a turbidite's spatial extent and thickness are a function of the local seismic intensity and can be used for reconstructing paleo-intensities. Consequently, our multilake turbidite record aids in pinpointing magnitudes, rupture locations, and extent of past subduction earthquakes in south central Chile. Comparison of the lacustrine turbidite records with historical reports, a paleotsunami/subsidence record, and a marine megaturbidite record demonstrates that the Valdivia Segment is characterized by a variable rupture mode over the last 900 years including (i) full ruptures (M w~9 .5: 1960, 1575, 1319 ± 9, 1127 ± 44), (ii) ruptures covering half of the Valdivia Segment (M w~9 : 1837), and (iii) partial ruptures of much smaller coseismic slip and extent (M w~7 .5-8: 1737, 1466 ± 4). Also, distant or smaller local earthquakes can leave a specific sedimentary imprint which may resolve subtle differences in seismic intensity values. For instance, the 2010 event at the Maule Segment produced higher seismic intensities toward southeastern localities compared to previous megathrust ruptures of similar size and extent near Concepciόn.

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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.

[1] The temporal and spatial evolution of a seismogenic megasplay fault in the Kumano area, Nankai Trough (southwest Japan), is revealed by detailed investigation of the three-dimensional structure of the shallow portions of the fault, combined with the results of drilling and dating of cores from Integrated Ocean Drilling Program (IODP) Expedition 316. The ENE striking eastern portion of the splay fault has remained active since the inception of faulting at ∼1.95 Ma. The recent shortening rate is ∼1 m/kyr, which represents ∼1.5%-2.5% of the total plate convergence rate of ∼40-65 m/kyr. The NE striking western portion of the splay fault exhibits a different mode of activity. Early stage activity (before 1.55 Ma) was similar to the eastern portion, but the fault was inactive between 1.55 and 1.24 Ma. The fault was reactivated for a short time at ∼1.24 Ma but again ceased activity after formation of the secondary branch and has been inactive since 1.24 Ma. Cessation of splay fault activity in the western domain after 1.55 Ma may be due to collision with a seamount and resulting bending of the accretionary prism in the splay fault footwall. Continuous activity of the eastern domain of the splay fault after 1.24 Ma may be related to geometrical favorability due to reorientation of the fault after the seamount passed beneath the imbricate thrust zone, leading to initiation of slightly oblique subduction.

[1] Multiple lines of evidence exist for a range of sediment mass movement processes within the shallow megasplay fault zone (MSFZ) area and the adjacent slope basin in the outer fore arc of the Nankai subduction zone, Japan. Diagnostic features observed in three-dimensional reflection seismic data and in cores of the Integrated Ocean Drilling Program (IODP) document a multifarious mass movement history spanning ∼2.87 million years. Various modes and scales of sediment remobilization can be related to the different morphotectonic settings in which they occurred. From this evidence, we decipher the tectonic control on slumping and mass transport deposition in the Nankai fore arc. Three periods of intensified mass wasting coincided with pulses of enhanced activity on the splay fault: (1) an initial phase of juvenile out-of-sequence thrusting ∼1.95 to 1.7 Ma, (2) a reactivation phase between ∼1.55 and 1.24 Ma, and (3) at about 1 Ma, during a phase of uplift of the fore-arc high and motion along the MSFZ. We suggest that slope oversteepening, extensional stress regimes, and lateral transmission of fluid overpressures may have preconditioned the slope sediments to fail. Individual mass-wasting events may have been triggered by dynamic loading from earthquake waves and/or transient pulses of pore pressure along the splay fault. Overall, our results provide insights into the complicated interplay between tectonic and submarine mass movement processes. We demonstrate that detailed knowledge about the spatial and temporal distribution of submarine mass movements can be integrated into a holistic reconstruction of tectonostratigraphic evolution of accretionary margins.