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Fault segmentation: New concepts from the Wasatch Fault Zone, Utah, USA
Author(s) -
DuRoss Christopher B.,
Personius Stephen F.,
Crone Anthony J.,
Olig Susan S.,
Hylland Michael D.,
Lund William R.,
Schwartz David P.
Publication year - 2016
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1002/2015jb012519
Subject(s) - seismology , geology , seismic hazard , fault (geology) , earthquake rupture , paleoseismology , active fault , holocene , slip (aerodynamics) , trench , tectonics , surface rupture , paleontology , chemistry , physics , organic chemistry , layer (electronics) , thermodynamics
The question of whether structural segment boundaries along multisegment normal faults such as the Wasatch fault zone (WFZ) act as persistent barriers to rupture is critical to seismic hazard analyses. We synthesized late Holocene paleoseismic data from 20 trench sites along the central WFZ to evaluate earthquake rupture length and fault segmentation. For the youngest (<3 ka) and best‐constrained earthquakes, differences in earthquake timing across prominent primary segment boundaries, especially for the most recent earthquakes on the north‐central WFZ, are consistent with segment‐controlled ruptures. However, broadly constrained earthquake times, dissimilar event times along the segments, the presence of smaller‐scale (subsegment) boundaries, and areas of complex faulting permit partial‐segment and multisegment (e.g., spillover) ruptures that are shorter (~20–40 km) or longer (~60–100 km) than the primary segment lengths (35–59 km). We report a segmented WFZ model that includes 24 earthquakes since ~7 ka and yields mean estimates of recurrence (1.1–1.3 kyr) and vertical slip rate (1.3–2.0 mm/yr) for the segments. However, additional rupture scenarios that include segment boundary spatial uncertainties, floating earthquakes, and multisegment ruptures are necessary to fully address epistemic uncertainties in rupture length. We compare the central WFZ to paleoseismic and historical surface ruptures in the Basin and Range Province and central Italian Apennines and conclude that displacement profiles have limited value for assessing the persistence of segment boundaries but can aid in interpreting prehistoric spillover ruptures. Our comparison also suggests that the probabilities of shorter and longer ruptures on the WFZ need to be investigated.