The 4 August 2004, Lake Ontario, Earthquake

Kim, WonYoung; Dineva, Savka; Ma, Shengwu; Eaton, David W.

doi:10.1785/gssrl.77.1.65

Cited by 18 publications

(15 citation statements)

References 42 publications

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“…New data are also added since data published elsewhere and from a previously unavailable dataset that had been maintained by the Alberta Geological Survey (AGS). The published data are compiled from a literature investigation of the following articles by Adams (1987), Balfour et al (2011, Bell and Bachu (2003), Buchbinder (1990), Du et al (2003), Eisbacher and Bielenstein (1971), Hamid (2008), Hurd and Zoback (2012), Konstantinovskaya et al (2012), Kim (2003), Kim et al (2006), Ma et al (2008), Mazzotti and Townend (2010), Michael and Buschkuehle (2008), Ruppert (2008), Steffen et al (2012), StLouisEQcenter (2010), Yassir and Dusseault (1992), and Zakharova and Goldberg (2014). The update adds up to 514 new records in Canada (Fig.…”

Section: Update Of the Canadian Stress Mapmentioning

confidence: 99%

A revised crustal stress orientation database for Canada

et al. 2014

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Section: Update Of the Canadian Stress Mapmentioning

confidence: 99%

A revised crustal stress orientation database for Canada

et al. 2014

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“…Although central and eastern North America constitute an intraplate setting, several large earthquakes have occurred there over the past three centuries (Bent, 1995(Bent, , 1996Du et al, 2003;Ebel, 2009;Horner et al, 1978;Horton et al, 2005;Hough & Page, 2011;Kim, 2003;Kim & Chapman, 2005;Kim et al, 2006;Ma et al, 2008;Neely et al, 2018;Sbar et al, 1975;Yang & Aggarwal, 1981). Most notable are the New Madrid earthquakes and their aftershocks that shook the Midwest between 1811 and 1812 and the 1886 Charleston earthquake in South Carolina.…”

Section: Introductionmentioning

confidence: 99%

Role of Large‐Scale Tectonic Forces in Intraplate Earthquakes of Central and Eastern North America

Ghosh

Holt

Bahadori

2019

Geochem Geophys Geosyst

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Central and eastern United States (CEUS) have experienced large intraplate earthquakes. Yet, at present there is no comprehensive model to explain stresses, strain, and seismicity in this intraplate setting. Models to explain the intraplate stresses in CEUS include glacio‐isostatic adjustment, ridge push effects, local stresses along preexisting fracture zones, and large‐scale convection. In this paper, we present a self‐consistent model of the dynamics of CEUS that explains the stress field responsible for these intraplate earthquakes. The earthquakes represent slow, ongoing deformation associated with forces arising from a combination of lithosphere topography and structure, together with the effects of density‐driven mantle flow. Using GPS data, we calculate strain rates that are likely to arise from tectonic effects and conclude that intraplate strain rates associated with tectonic effects are unlikely to exceed 1 × 10−9 year−1. We test several models of lateral viscosity variations by comparing model stress orientation output with earthquake moment tensors, SHmax directions from stress inversion, and P axes of earthquakes. A model that satisfies stress and earthquake constraints and also strain rate magnitude constraints requires high viscosity (1025 Pa·s) craton and old oceanic lithosphere of the western Atlantic block and weaker (5 × 1024 Pa·s) accreted Appalachian terrane. Other strength contrasts within the lithosphere are likely present. Incorporation of these into future models using constraints from seismology, along with refined geodetic measurements and improved estimates of crust and upper mantle densities, is needed to further refine long‐term dynamic models and better evaluate the hazards associated with this very slow, ongoing permanent deformation within the eastern and central United States.

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“…For example, the depth of the earthquake on August 4, 2004 beneath Lake Ontario, North America, is only 4 km, and is believed to occur within the Precambrian basement. Depth of the shallowest earthquake is only about 1 km [12,13]. However, there are neither surface ruptures nor obvious faults asscoited with them.…”

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A shallow aftershock sequence in the north-eastern end of the Wenchuan earthquake aftershock zone

Luo

Zeng

et al. 2010

Sci. China Earth Sci.

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Previous studies show that mature faults are filled with fault gouge in the shallow part and thus cannot accumulate enough strain energy for earthquakes. Therefore most earthquakes are deeper than 5 km, except those events occurring on new faults or in intact rocks. From field observation, Wenchuan earthquake is found to rupture the free surface about 200 km, but the rupture may extend underground much further from teleseismic body waves inversion and aftershocks distribution. In the northeastern end of the rupture zone, deep rupture may induce stress increase near the free surface, and trigger shallow earthquakes. An M s 5.7 aftershock occurred at Qingchuan, northeast end of Wenchuan earthquake fault on July 24, 2008, featuring thrust mechanism with a 3 km source centroid depth. The shallow focal depth is confirmed with the sPL phase recorded at station L0205. As Rayleigh wave is well only developed for source depth less than 1/5 of epicentral distance, the observed large amplitude of Rg at a distance of 15 km implied depth of 3 km or less. Dozens of aftershocks' sPL waveforms are also analyzed to confirm the source depths less than 3 km. On the other hand, no surface ruptures are found by geological survey or InSAR studies. It is strongly suggested that these aftershock sequences initiate fresh rupture in intact rocks triggered by stress increase from the deep co-seismic rupture of the Wenchuan mainshock.Wenchuan earthquake, shallow earthquake, focal depth, wave modeling Citation:Luo Y, Ni S D, Zeng X F, et al. A shallow aftershock sequence in the north-eastern end of the Wenchuan earthquake aftershock zone.On May 12, 2008, an M s 8.0 earthquake occurred at Wenchuan, Sichuan Province, and caused heavy economic loss and casualties. Dozens of strong aftershocks with magnitude ≥5.0 occurred along the Longmenshan faults in the following months. The depth and focal mechanism of the aftershock sequence provided a good constraint on mainshock fault and regional stress field. Focal depth is an important parameter to study regional seismicity and seismic hazard, and also plays a particularly important role in understanding the relationship between seismicity and geological structure. Depths of most intraplate earthquakes are between 5 and 25 km [1][2][3][4]. When depth is larger than 25 km, it is not very easy to accumulate strain because of ductile deformation in the lower crust. When depth is less than 5 km, mature faults are filled with soft fault gouge in the upper part; thus, it is difficult to accumulate enough strain. Recent studies show that the depths of Wenchuan earthquake aftershocks are mostly in the range of 5-20 km [5][6][7][8][9][10]. But in many regions, especially inside an old stable intraplate such as southwest part of Australia (Merkering) and North America, nearsurface stress measurements in the area show relatively high deviatoric stress. Because of strong strength in cold and old

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The 4 August 2004, Lake Ontario, Earthquake

Abstract: A M w 3.

Cited by 18 publications

References 42 publications

A revised crustal stress orientation database for Canada

A revised crustal stress orientation database for Canada

Role of Large‐Scale Tectonic Forces in Intraplate Earthquakes of Central and Eastern North America

A shallow aftershock sequence in the north-eastern end of the Wenchuan earthquake aftershock zone

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