Review of "The Ulakhan fault surface rupture and the seismicity of the Okhotsk-North America plate boundary" by Hindle et al.

2018 ◽  
Author(s):  
Anonymous
Keyword(s):  
North America ◽  
Plate Boundary ◽  
Surface Rupture ◽  
Fault Surface

scholarly journals The Ulakhan fault surface rupture and the seismicity of the Okhotsk–North America plate boundary

Solid Earth ◽  
2019 ◽  
Vol 10 (2) ◽  
pp. 561-580 ◽  
Author(s):  
David Hindle ◽  
Boris Sedov ◽  
Susanne Lindauer ◽  
Kevin Mackey
Keyword(s):  
North America ◽  
Plate Tectonics ◽  
Plate Boundary ◽  
Slip Rate ◽  
Field Work ◽  
Alluvial Fan ◽  
Age Dating ◽  
Aerial Photographs ◽  
Fault System ◽  
Fault Surface

Abstract. New field work, combined with analysis of high-resolution aerial photographs, digital elevation models, and satellite imagery, has identified an active fault that is traceable for ∼90 km across the Seymchan Basin and is part of the Ulakhan fault system, which is believed to form the Okhotsk–North America plate boundary. Age dating of alluvial fan sediments in a channel system that is disturbed by fault activity suggests the current scarp is a result of a series of large earthquakes (≥Mw 7.5) that have occurred since 11.6±2.7 ka. A possible channel feature offset by 62±4 m associated with these sediments yields a slip rate of 5.3±1.3 mm yr−1, in broad agreement with rates suggested from global plate tectonics. Our results clearly identify the Ulakhan fault as the Okhotsk–North America plate boundary and show that tectonic strain release is strongly concentrated on the boundaries of Okhotsk. In light of our results, the likelihood of recurrence of Mw 7.5 earthquakes is high, suggesting a previously underestimated seismic hazard across the region.

scholarly journals The Ulakhan fault surface rupture and the seismicity of the Okhotsk-North America plate boundary

2018 ◽  
Author(s):  
David Hindle ◽  
Boris Sedov ◽  
Susanne Lindauer ◽  
Kevin Mackey
Keyword(s):  
North America ◽  
Plate Tectonics ◽  
Plate Boundary ◽  
Slip Rate ◽  
Field Work ◽  
Alluvial Fan ◽  
Age Dating ◽  
Aerial Photographs ◽  
Fault System ◽  
Fault Surface

Abstract. New field work, combined with analysis of aerial photographs, high resolution, digital elevation models, and satellite imagery has identified an active fault that is traceable for ∼ 90 km across the Seymchan Basin, and is part of the Ulakhan fault system, which is believed to form the Okhtotsk-North America plate boundary. Age dating of alluvial fan sediments in a channel system that is disturbed by and abandoned due to fault activity, suggest the current scarp is a result of a series of large earthquakes (≥ Mw 7.5) that have occurred since ∼11.5 ka. A possible offset channel edge associated with these sediments yields a slip rate of ∼ 5–6 mm yr−1, in broad agreement with rates suggested from global plate tectonics and other theoretical studies. Our results clearly identify the Ulakhan fault as the Okhotsk-North America plate boundary, and show that tectonic strain release is strongly concentrated on the boundaries of Okhotsk. In the light of our results, the likelihood of recurrence of Mw 7.5 earthquakes is high, raising serious questions of seismic hazard across the region.

scholarly journals Distribution of the Pacific/North America motion in the Queen Charlotte Islands-S. Alaska plate boundary zone

2003 ◽  
Vol 30 (14) ◽  
Author(s):  
Stéphane Mazzotti ◽  
Roy D. Hyndman ◽  
Paul Flück ◽  
Alex J. Smith ◽  
Michael Schmidt
Keyword(s):  
North America ◽  
Plate Boundary ◽  
Boundary Zone ◽  
Queen Charlotte Islands ◽  
The Pacific ◽  
Plate Boundary Zone

scholarly journals Surface rupture in stochastic slip models

2020 ◽  
Vol 221 (2) ◽  
pp. 1081-1089 ◽  
Author(s):  
S Murphy ◽  
A Herrero
Keyword(s):  
Probability Density Function ◽  
Probability Density ◽  
Density Function ◽  
Source Model ◽  
Surface Rupture ◽  
Size Frequency Distribution ◽  
Fault Surface ◽  
Planar Fault ◽  
Small Change ◽  
Composite Source Model

SUMMARY As an alternative to spectral methods, stochastic self-similar slip can be produced through a composite source model by placing a power-law scaling size-frequency distribution of circular slip dislocations on a fault surface. However these models do not accurately account for observed surface rupture behaviour. We propose a modification to the composite source model that corrects this issue. The advantage of this technique is that it accommodates the use of fractal slip distributions on non-planar fault surfaces. However to mimic a surface rupture using this technique, releasing the boundary condition at the top of the fault, we observed a systematic decrease in slip at shallow depths. We propose a new strategy whereby the surface is treated like a reflector with the slip being folded back onto the fault. Two different techniques based on this principal are presented: the first is the method of images. It requires a small change to pre-existing codes and works for planar faults. The second involves the use of a multistage trilateration technique. It is applied to non-planar faults described by an unstructured mesh. The reflected slip calculated using the two techniques is near identical on a planar fault, suggesting they are equivalent. Applying this correction, where reflected slip is accounted for in the composite source model, the lack of slip at shallow depths is not observed any more and there is no systematic trend with depth. However, there are other parameters which may affect the spatial distribution of slip across the fault plane. For example, the type of probability density function used in the placement of the subevent is also important. In the case where the location of maximum slip is known to a first order, a Gaussian may be appropriate to describe the probability function. For hazard assessment studies a uniform probability density function is more suitable as it provides no underlying systematic spatial trend.

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