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Bridge Management Objectives and Methodologies
Published in J.E. Harding, G.E.R. Parke, M.J. Ryall, Bridge Management 3, 2014
The Tacoma Narrows Bridge is located in a very seismically active area. The seismicity of the area is controlled by the interaction of the converging Juan de Fuca Plate and the North American Plate. The boundary between these two plates is the Cascadia Subduction Zone. During the pre-Tertiary and the Tertiary, various bedrock terrains have been subducted along the zone and overridden by the North American Plate. The bridge site itself is underlain by a thick accumulation of unconsolidated sediments that are in turn underlain by consolidated sediments and bedrock units of uncertain thickness.
Numerical analyses for seismic retrofit design Lions Gate Bridge, Vancouver, British Columbia
Published in Christine Detournay, Roger Hart, FLAC and Numerical Modeling in Geomechanics, 2020
South-western British Columbia is an area of active seismicity. The oceanic Juan de Fuca plate is subducting under the North American continental plate. This results in stresses within and between the plates and periodic earthquakes. Earthquake sources include those within the crust of the North American plate, intra-plate earthquakes within the subductucting Juan de Fuca plate, and inter-plate subduction earthquakes.
Influence of ground motion duration on the seismic vulnerability of aging highway bridges
Published in Structure and Infrastructure Engineering, 2023
Bhaskar Panchireddi, Shivang Shekhar, Jayadipta Ghosh
Several past studies on ground motion modelling (Bard & Bouchon, 1980; Olsen, Stephenson, & Geisselmeyer, 2008) reveals that earthquakes within the geographical region of Seattle could be damaging for local civil engineering structures. Located within the Cascadia subduction zone along the Pacific Northwest Coast of the United States, Seattle is susceptible to experience long duration and large magnitude earthquakes in addition to less-damaging seismic shaking. For instance, the Seattle fault zone comprises of a network of crustal or shallow earthquakes that occur in the North American plate at 0–30 km from the crust’s surface along the fault and typically results in less-intense seismic shaking with moment magnitude Mw < 7.0; even though crustal earthquakes with Mw = 7.5 has also been documented. On the other hand, the interface between the North American plate and the San Juan de Fuca plate extending from Northern California to British Columbia is known to generate subduction or megathrust earthquakes. Compared to the crustal counterpart, these subduction earthquakes are substantially more intense with moment magnitudes that can exceed 9.0. As the largest city in both the state of Washington and the Pacific Northwest region of North America, such earthquake occurrences in Seattle are expected to have consequences that are prolonged and catastrophic.
Seismic Performance and Collapse Fragility of Balloon-Framed CLT School Building
Published in Journal of Earthquake Engineering, 2023
Yuxin Pan, Md Shahnewaz, Thomas Tannert
To perform NLTHA and IDA on a 3D model, appropriate bi-directional ground motion records that represent the characteristic seismicity of the location need to be selected. The building site, Vancouver, BC, is located in an active seismic region, called the Cascadia Subduction Zone (Pan, Ventura, and Tannert 2020). The local seismicity is dominated by the subduction of the Juan de Fuca plate beneath the continental North American plate. The earthquake hazard is contributed by three sources: (1) shallow crustal earthquakes within the crust of the North American plate; (2) subduction inslab earthquakes within the sinking Juan de Fuca plate; and (3) subduction interface earthquakes at the interface of two plates (Adams et al. 2015).
Stochastic source modeling and tsunami simulations of cascadia subduction earthquakes for Canadian Pacific coast
Published in Coastal Engineering Journal, 2022
Canada’s Pacific coast has a high likelihood of facing significant seismic and tsunami hazards from the Cascadia subduction zone (CSZ) in the future (Hyndman and Rogers 2010). The CSZ is the result of the subduction of the Juan de Fuca Plate, Gorda Plate, and Explorer Plate underneath the North American Plate (Figure 1). The CSZ extends 1,100 km along the coastal margin from Vancouver Island, British Columbia, Canada, to the Mendocino Escarpment, Northern California, United States, and has a convergence rate of 30 to 41 mm/year (Mazzotti et al. 2003; DeMets, Gordon, and Argus 2010; see the relative plate motion arrows in Figure 1). In the past, the CSZ ruptured in great megathrust earthquakes of moment magnitude (Mw) 8+, having recurrence periods between 100 to 800 years (Petersen, Cramer, and Frankel 2002) with an average recurrence period of 530 years for the full-margin rupture (Goldfinger et al. 2012). Evidence of these Holocene megathrust earthquakes is preserved along the northwestern Pacific coast (Atwater and Hemphill-Haley 1997; Hawkes et al. 2011). The last major earthquake occurred in 1700 with Mw9 (Satake, Wang, and Atwater 2003; Atwater et al. 2015), which ruptured the entire subduction margin. Evidence for the 1700 tsunami came from First Nation’s myths in North America and written documents that recorded flooding damages in Japan (Satake et al. 1996). The sedimentary records of the CSZ events can be seen in the form of marine turbidite deposits (Goldfinger et al. 2012) and buried soil/marsh data (Atwater et al. 2015). Thus, the CSZ has potential to rupture in a sizable subduction earthquake, posing an imminent threat of a possible tsunami, which will cause catastrophic damage to highly populated areas along the Pacific coast.