Ground Motion in the Presence of Complex Topography II: Earthquake Sources and 3D Simulations

Cascadia Onshore‐Offshore Site Response, Submarine Sediment Mobilization, and Earthquake Recurrence

“…Additionally, deamplification may occur within depressions, as well as due to scattering related to topography. Hartzell et al () verify these results observationally, finding amplification of a factor of 3 atop a peak in the San Francisco area. In a number of regions, topographic gradients and other topographic attributes have been found to correlate statistically with the average shear wave velocity in the upper 30 m, or V s 30 , which is a widely used proxy for site response (Wald & Allen, ; Yong et al, ).…”

“…Herein, “inherent variability” is synonymous with “site response” or “site effects” and refers to the changes in shaking at a particular location caused by nearby geologic structure, relative to the shaking at some reference. Numerous terrestrial studies show that site response may manifest as variations in shaking amplitudes of factors of a few percent to an order of magnitude or more (Bowden & Tsai, ; Frankel, Carver, & Williams, ; Frankel, Stephenson, & Carver, ; Furumura & Hayakawa, ; Hartzell et al, ; Nakamura et al, ).…”

“…Site response has been shown to correlate with geology, topographic elevation, and gradients (Hartzell et al, ), with correlations that vary depending on geologic or tectonic environment (Ahdi et al, ). Mostly terrestrial studies have demonstrated that some geologic structures have natural resonance frequencies, such as steep mountains, sediment‐filled basin, wedges, and canyons (Bard & Bouchon, ; Volk et al, ).…”

“…Topography also may significantly alter shaking locally. Hartzell et al () noted that, in general, amplification is likely when wavelengths are comparable to the width of the topographic peak, L , such that resonance occurs at frequency f ~ V / L , ( V is the shear wave velocity) and by a greater amount as the slope increases and incidence angle decreases. Additionally, deamplification may occur within depressions, as well as due to scattering related to topography.…”

Small-scale scattering heterogeneities beneath the northern Tien Shan from the teleseismic P wavefield

“…Thus more seismic data containing three-component waveforms are needed to compare results from these two approaches. Although coda waves can be strongly excited by scattering due to surface topography (e.g., Imperatori and Mai 2015;Takemura et al 2015;Hartzell et al 2017), the relative contribution of topographic scattering in the high-frequency wavefield is only approximately 12% (Takemura et al 2015) in local areas. However, scattering due to surface topography cannot be completely ruled out on generating the teleseismic P-wave coda, a more realistic numerical hybrid method (Monteiller et al 2013) is needed to model these effects in the future research.…”