Radiocarbon evidence for extensive plate-boundary rupture about 300 years ago at the Cascadia subduction zone

Fujiwara

et al. 2016

Earth-Science Reviews

Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. ABSTRACTThe Nankai-Suruga Trough, the subduction zone that lies immediately south of Japan's densely populated southern coastline, generates devastating great earthquakes (magnitude > 8) characterised by intense shaking, crustal deformation and tsunami generation. Forecasting the hazards associated with future earthquakes along this >700 km long fault requires a comprehensive understanding of past fault behaviour. While the region benefits from a long and detailed historical record, palaeoseismology has the potential to provide a longer-term perspective and additional crucial insights. In this paper, we summarise the current state of knowledge regarding geological evidence for past earthquakes and tsunamis along the Nankai-Suruga Trough. Incorporating literature originally published in both Japanese and English and enhancing available results with new age modelling approaches, we summarise and critically evaluate evidence from a wide variety of sources. Palaeoseismic evidence includes uplifted marine terraces and biota, marine and lacustrine turbidites, liquefaction features, subsided marshes and tsunami deposits in coastal lakes and lowlands. While 75 publications describe proposed evidence from more than 70 sites, only a limited number provide compelling, well-dated evidence. The best available records enable us to map the most likely rupture zones of twelve earthquakes that occurred during the historical period. This spatiotemporal compilation suggests that the AD 1707 earthquake ruptured almost the full length of the subduction zone and that earthquakes in AD 1361 and 684 may have been predecessors of similar magnitude. Intervening earthquakes were of lesser magnitude, highlighting the variability in rupture mode that characterises the Nankai-Suruga Trough. Intervals between ruptures of the same seismic segment range from less than 100 to more than 450 years during the historical period. Over longer timescales, palaeoseismic evidence suggests intervals between earthquakes ranging from 100 to 700 years, however these figures reflect a range of thresholds controlling the creation and preservation of evidence at any given site as well as the genuine intervals between earthquakes. At present, there is no geological data that suggest the occurrence of a larger magnitude earthquake than that experienced in AD 1707, however few studies have sought to establish the relative magnitudes of different earthquake and tsunami events along the Nankai-Suruga Trough. Alongside the lack of...

Section: Chronological Controlmentioning

confidence: 99%

A systematic review of geological evidence for Holocene earthquakes and tsunamis along the Nankai-Suruga Trough, Japan

Fujiwara

et al. 2016

Earth-Science Reviews

“…Geological evidence discussed above suggests that some earthquakes have ruptured hundreds of kilometers of the Cascadia margin and that the entire subduction zone may have ruptured during the last great earthquake about 300 years ago [Nelson et al, 1995] …”

Section: Size Of Plate Boundary Earthquakesmentioning

confidence: 99%

Evidence for large earthquakes at the Cascadia Subduction Zone

Clague¹

1997

Reviews of Geophysics

Self Cite

177

Abstract. Large, historically unprecedented earthquakes at the Cascadia subduction zone in western North America have left signs of sudden land level change, tsunamis, and strong shaking in coastal sediments. The coastal geological evidence suggests that many of the earthquakes occurred at the boundary between the overriding North American plate and the subducting Juan de Fuca plate. This hypothesis is consistent with geodetic measurements and the results of geophysical modeling, which indicate that part of the plate boundary is locked and accumulating elastic strain that will be released during a future large earthquake. Arguments based on potential amounts of seismic slip and likely rupture areas suggest that most or all of the plate boundary earthquakes were magnitude 8 or larger events. The last earthquake or series of earthquakes, about 300 years ago, ruptured the entire 1000-km length of the subduction zone; if it was a single quake, it probably exceeded magnitude 9. Other earthquakes may have ruptured one or more segments of the subduction zone Or may have occurred on faults in the North American plate. Recurrence intervals are uncertain because of difficulties in identifying and dating earthquakes. In southwestern Washington state, intervals for the seven most recent earthquakes average about 500 years but range from less than 200 years to 700-1300 years. Future research on Cascadian plate boundary earthquakes will probably focus on (1) the relation between plate boundary and crustal earthquakes, (2) earthquake magnitude, (3) the areal extent and severity of seismic ground motions, (4) ages and number of past plate boundary earthquakes, and (5) land level changes preceding earthquakes.

“…Key contributions to practical earthquake hazard assessment include the identification of great (magnitude 8 or 9) earthquakes during the Holocene where there is no historical record (Atwater, 1987); earthquakes of substantially greater magnitude than directly observed (Minoura et al, 2001;Sawai et al, 2008); estimating recurrence intervals of great earthquakes (Atwater and HemphillHaley, 1997;Nelson et al, 1995); and defining different patterns of rupture along a subduction zone (Cisternas et al, 2005;Kelsey et al, 2002;Nelson et al, 2006;Sawai et al, 2004). Since publication of the seminal paper (Atwater, 1987), and widespread adoption of well-tested field and analytical methods (e.g.…”

Section: Introduction and Structure Of The Papermentioning

confidence: 99%

Detection limits of tidal-wetland sequences to identify variable rupture modes of megathrust earthquakes

Shennan

Quaternary Science Reviews

Barlow

2016

Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. earthquakes. We conclude that coastal paleoseismological studies benefit from a methodological framework that employs rigorous evaluation of five essential criteria and a sixth which may be very robust but only occur at some sites: 1 -lateral extent of peat-mud or mud-peat couplets with sharp contacts; 2 -suddenness of submergence or emergence, and replicated within each site; 3 -amount of vertical motion, quantified with 95% error terms and replicated within each site; 4 -syncroneity of submergence and emergence based on statistical age modelling; 5 -spatial pattern of submergence and emergence; 6 -possible additional evidence, such as evidence of a tsunami or liquefaction concurrent with submergence or emergence. We suggest that it is possible to consider detection limits as low as 0.1 to 0.2 m coseismic vertical change. Introduction and structure of the paperCoastal paleoseismology provides critical information that helps to improve understanding and modelling of seismic hazards, including associated tsunami, at all major subduction zones. Key contributions to practical earthquake hazard assessment include the identification of great (magnitude 8 or 9) earthquakes during the Holocene where there is no historical record (Atwater, 1987); earthquakes of substantially greater magnitude than directly observed (Minoura et al., 2001;Sawai et al., 2008); estimating recurrence intervals of great earthquakes (Atwater and HemphillHaley, 1997;Nelson et al., 1995); and defining different patterns of rupture along a subduction zone (Cisternas et al., 2005;Kelsey et al., 2002;Nelson et al., 2006;Sawai et al., 2004). Since publication of the seminal paper (Atwater, 1987), and widespread adoption of well-tested field and analytical methods (e.g. Atwater and Hemphill-Haley, 1997;Hayward et al., 2006;Kelsey, 2015;Nelson, 2015;Nelson et al., 1996;Witter, 2015) debate moved on to questions critical for hazard assessment, emergency planning and international building code design (Mueller et al., 2015;Wesson et al., 2007). Key questions include the extent of past great earthquake ruptures (a proxy for magnitude), the identification of the boundaries between rupture segments, the persistence of these boundaries over multiple earthquake cycles, recurrence intervals of great earthquakes in each segment, the role of aseismic slip, and whether segments of plate boundaries that are currently creeping can generate great earthquakes Goldfinger et al., 2012;Hayward et al., 2015;Kelsey et al., 2015;Mueller...