Publication Date:
2017-05-17
Description:
The thickness of an active plate boundary fault is an important parameter for understanding
the strength and spatial heterogeneity of fault behavior. We have compiled direct
measurements of the thickness of subduction thrust faults from active and ancient examples
observed by ocean drilling and fi eld studies in accretionary wedges. We describe a general
geometric model for subduction thrust décollements, which includes multiple simultaneously
active, anastomosing fault strands tens of meters thick. The total thickness encompassing all
simultaneously active strands increases to ~100–350 m at ~1–2 km below seafl oor, and this
thickness is maintained down to a depth of ~15 km. Thin sharp faults representing earthquake
slip surfaces or other discrete slip events are found within and along the edges of the tens-ofmeters-
thick fault strands. Although fl attening, primary inherited chaotic fabrics, and fault
migration through subducting sediments or the frontal prism may build mélange sections that
are much thicker (to several kilometers), this thickness does not describe the active fault at
any depth. These observations suggest that models should treat the subduction thrust plate
boundary fault as 〈1–20 cm thick during earthquakes, with a concentration of postseismic
and interseismic creep in single to several strands 5–35 m thick, with lesser distributed interseismic
deformation in stratally disrupted rocks surrounding the fault strands.
Type:
Article
,
PeerReviewed
Format:
text
Format:
text
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