2012 Haida Gwaii Quake: Insight Into Cascadia's Subduction Extent

Szeliga, Walter

doi:10.1002/2013eo090001

Cited by 11 publications

(10 citation statements)

References 14 publications

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“…This form of partitioning is similar in geometry and scale to that suggested for Haida Gwaii, in the Cascadia subduction zone (Lay et al 2013;Szeliga 2013), where a large, reverse-faulting earthquake occurred in October 2012. The interpretation that the Pliny and Strabo Trenches are the expressions of reverse faulting also provides a possible source location for the AD 1303 earthquake, which historical data suggest occurred in the Hellenic Arc, somewhere between Crete and Rhodes (Ambraseys 2009;Yolsal-Ç evikbilen & Taymaz 2012).…”

Section: Accommodation Of Motion Near the Pliny And Strabo Trenchessupporting

confidence: 65%

Late Holocene uplift of Rhodes, Greece: evidence for a large tsunamigenic earthquake and the implications for the tectonics of the eastern Hellenic Trench System

Howell¹,

Jackson²,

England

et al. 2015

Geophys. J. Int.

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S U M M A R YSeveral large earthquakes in the Hellenic subduction zone have been documented in historical records from around the eastern Mediterranean, but the relative seismic quiescence of the region over the period of instrumental observation means that the exact locations of these earthquakes and their tectonic significance are not known. We present AMS radiocarbon dates from uplifted late Holocene palaeoshorelines from the island of Rhodes, showing that uplift is most consistent with a single large (M W ≥ 7.7) reverse-faulting earthquake between about 2000 BC and 200 BC. Analysis of the uplift treating the earthquake as a dislocation in an elastic half-space shows a predominantly reverse-faulting event with a slip vector oblique to the direction of convergence between Rhodes and Nubia. We suggest that the fault responsible for the uplift dips at an angle of 30-60• above the more gently dipping oblique subduction interface. The highly oblique convergence across the eastern Hellenic plate boundary zone appears to be partitioned into reverse slip on faults that strike parallel to the boundary and strike-parallel or oblique slip on the subduction interface. Hydrodynamical simulation of tsunami propagation from a range of tectonically plausible sources suggests that earthquakes on the fault uplifting Rhodes represent a significant tsunami hazard for Rhodes and SW Turkey, and also possibly for Cyprus and the Nile Delta.

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Section: Accommodation Of Motion Near the Pliny And Strabo Trenchessupporting

confidence: 65%

Late Holocene uplift of Rhodes, Greece: evidence for a large tsunamigenic earthquake and the implications for the tectonics of the eastern Hellenic Trench System

Howell¹,

Jackson²,

England

et al. 2015

Geophys. J. Int.

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“…To the north of the Cascadia subduction zone, displacements along the dextral Queen Charlotte-Fairweather fault average between 43 and 55 mm a À1 (Clague, 1989a;Elliott et al, 2010). Following the 2012 Haida Gwaii earthquake, Szeliga (2013) argued that the northern end of subduction along the Cascadia margin may need to be redefined, as the primarily strike-slip Queen Charlotte Fault has a smaller component of convergence. Early GPS position data collected during that earthquake indicate a meter of coseismic displacement toward the rupture, followed by more than 1 mm d À1 of postseismic strain (James et al, 2013).…”

Section: Regional Tectonic Regimementioning

confidence: 99%

“…Although recent studies into the 2012 Haida Gwaii earthquake have documented a component of convergence along the predominantly strike-slip Queen Charlotte Fault (James et al, 2013;Lay et al, 2013;Szeliga, 2013), it is not known whether this has had a significant effect on RSL fluctuations since the LGM.…”

Section: Outer Islands-north Coastmentioning

confidence: 99%

Post-glacial sea-level change along the Pacific coast of North America

Shugar

Walker

Lian

et al. 2014

Quaternary Science Reviews

128

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a b s t r a c tSea-level history since the Last Glacial Maximum on the Pacific margin of North America is complex and heterogeneous owing to regional differences in crustal deformation (neotectonics), changes in global ocean volumes (eustasy) and the depression and rebound of the Earth's crust in response to ice sheets on land (isostasy). At the Last Glacial Maximum, the Cordilleran Ice Sheet depressed the crust over which it formed and created a raised forebulge along peripheral areas offshore. This, combined with different tectonic settings along the coast, resulted in divergent relative sea-level responses during the Holocene. For example, sea level was up to 200 m higher than present in the lower Fraser Valley region of southwest British Columbia, due largely to isostatic depression. At the same time, sea level was 150 m lower than present in Haida Gwaii, on the northern coast of British Columbia, due to the combined effects of the forebulge raising the land and lower eustatic sea level. A forebulge also developed in parts of southeast Alaska resulting in post-glacial sea levels at least 122 m lower than present and possibly as low as 165 m. On the coasts of Washington and Oregon, as well as south-central Alaska, neotectonics and eustasy seem to have played larger roles than isostatic adjustments in controlling relative sea-level changes.

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“…Shaking from this event lasted over two minutes and was felt over 1200 km away in Alberta, Canada (James et al, 2013;Szeliga, 2013;Cassidy et al, 2014). Based on finite-fault inversions and aftershock distributions, this thrust earthquake ruptured more than 140 km along the continental margin beneath the Queen Charlotte terrace (QCT) (Fig.…”

Section: Introductionmentioning

confidence: 99%

“…However, before 2012 the paucity of large earthquakes in the region from 51.7°to 52.4°N made it difficult to characterize the style of rupture (Rogers, 1983(Rogers, , 1986Nishenko and Jacob, 1990;Bufe, 2005). As the 2012 mainshock was large enough to be well-recorded globally, it provides a wealth of data with which to study this young subduction zone (Szeliga, 2013;Cassidy et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

Rupture Process of the 2012 Mw 7.8 Haida Gwaii Earthquake from an Empirical Green's Function Method

Hobbs¹,

Cassidy²,

Dosso³

2015

Bulletin of the Seismological Society of America

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This article examines rupture processes of the 28 October 2012 M w 7.8Haida Gwaii earthquake off the coast of British Columbia, Canada, using an empirical Green's function (EGF) technique. The Haida Gwaii earthquake was the largest event along the Canadian portion of the Pacific-North American plate boundary since the M s 8.1 Queen Charlotte earthquake of 1949. It occurred along a potentially blind thrust fault dipping gently to the northeast rather than the main, subvertical Queen Charlotte fault. Surface waveforms from a 2001 M w 6.3 event, located only 15 km from the 2012 epicenter and with similar mechanism, are used as an EGF and deconvolved from those of the 2012 mainshock. The resulting source time functions contain minimal path effects, focal mechanism effects, and instrument response, so the waveforms display only properties of the 2012 mainshock rupture itself. By examining azimuthal variations in these source time functions, we constrain parameters such as average rupture velocity, extent, and directivity. In addition, information is obtained about the possible existence of major subevents and their relative locations. Results indicate two subevents within this rupture, the first 12 km south and updip of the epicenter and the second approximately 28 km from the first along a heading parallel to the Queen Charlotte terrace (∼323°). Overall, the rupture front propagated roughly 50 km at an azimuth of 308.5°. This evidence for directivity to the northwest is important, given that earthquakes with strong directivity, such as the 2002 M w 7.9 Denali earthquake, have been shown to be capable of triggering earthquakes thousands of kilometers away. In this case, we suggest that northwest directivity of this earthquake is responsible for amplification of surface waves observed at seismic stations in Alaska (Gomberg, 2013) and may provide a potential link between this 2012 event and the 2013 Craig, Alaska, earthquake.Online Material: Figure of all relative source time functions used in directivity analysis.

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2012 Haida Gwaii Quake: Insight Into Cascadia's Subduction Extent

Cited by 11 publications

References 14 publications

Late Holocene uplift of Rhodes, Greece: evidence for a large tsunamigenic earthquake and the implications for the tectonics of the eastern Hellenic Trench System

Late Holocene uplift of Rhodes, Greece: evidence for a large tsunamigenic earthquake and the implications for the tectonics of the eastern Hellenic Trench System

Post-glacial sea-level change along the Pacific coast of North America

Rupture Process of the 2012 Mw 7.8 Haida Gwaii Earthquake from an Empirical Green's Function Method

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