Structure and seismic hazard of the ventura avenue anticline and ventura fault, California : prospect for large, multisegment ruptures in the western transverse ranges

The Ventura Avenue anticline is one of the fastest uplifting structures in southern California, rising at ∼5  mm/yr. We use well data and seismic reflection profiles to show that the anticline is underlain by the Ventura fault, which extends to seismogenic depth. Fault offset increases with depth, i...

Full description

Saved in:
Bibliographic Details
Main Authors: Hubbard, Judith, Shaw, John H., Dolan, James, Pratt, Thomas L., McAuliffe, Lee, Rockwell, Thomas K.
Other Authors: Earth Observatory of Singapore
Format: Article
Language:English
Published: 2014
Subjects:
Online Access:https://hdl.handle.net/10356/104839
http://hdl.handle.net/10220/20351
Tags: Add Tag
No Tags, Be the first to tag this record!
Institution: Nanyang Technological University
Language: English
id sg-ntu-dr.10356-104839
record_format dspace
spelling sg-ntu-dr.10356-1048392020-09-26T21:34:31Z Structure and seismic hazard of the ventura avenue anticline and ventura fault, California : prospect for large, multisegment ruptures in the western transverse ranges Hubbard, Judith Shaw, John H. Dolan, James Pratt, Thomas L. McAuliffe, Lee Rockwell, Thomas K. Earth Observatory of Singapore DRNTU::Science::Geology::Volcanoes and earthquakes The Ventura Avenue anticline is one of the fastest uplifting structures in southern California, rising at ∼5  mm/yr. We use well data and seismic reflection profiles to show that the anticline is underlain by the Ventura fault, which extends to seismogenic depth. Fault offset increases with depth, implying that the Ventura Avenue anticline is a fault‐propagation fold. A decrease in the uplift rate since ∼30±10  ka is consistent with the Ventura fault breaking through to the surface at that time and implies that the fault has a recent dip‐slip rate of ∼4.4–6.9  mm/yr. To the west, the Ventura fault and fold trend continues offshore as the Pitas Point fault and its associated hanging wall anticline. The Ventura–Pitas Point fault appears to flatten at about 7.5 km depth to a detachment, called the Sisar decollement, then step down on a blind thrust fault to the north. Other regional faults, including the San Cayetano and Red Mountain faults, link with this system at depth. We suggest that below 7.5 km, these faults may form a nearly continuous surface, posing the threat of large, multisegment earthquakes. Holocene marine terraces on the Ventura Avenue anticline suggest that it grows in discrete events with 5–10 m of uplift, with the latest event having occurred ∼800 years ago (Rockwell, 2011). Uplift this large would require large earthquakes (Mw 7.7–8.1) involving the entire Ventura/Pitas Point system and possibly more structures along strike, such as the San Cayetano fault. Because of the local geography and geology, such events would be associated with significant ground shaking amplification and regional tsunamis. Published Version 2014-08-20T02:40:13Z 2019-12-06T21:40:56Z 2014-08-20T02:40:13Z 2019-12-06T21:40:56Z 2014 2014 Journal Article Hubbard, J., Shaw, J. H., Dolan, J., Pratt, T. L., McAuliffe, L., & Rockwell, T. K. (2014). Structure and Seismic Hazard of the Ventura Avenue Anticline and Ventura Fault, California: Prospect for Large, Multisegment Ruptures in the Western Transverse Ranges. Bulletin of the Seismological Society of America, 104(3), 1070-1087. 0037-1106 https://hdl.handle.net/10356/104839 http://hdl.handle.net/10220/20351 10.1785/0120130125 en Bulletin of the seismological society of America © 2014 Seismological Society of America. This paper was published in Bulletin of the Seismological Society of America and is made available as an electronic reprint (preprint) with permission of Seismological Society of America. The paper can be found at the following official DOI: [http://dx.doi.org/ 10.1785/0120130125]. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper is prohibited and is subject to penalties under law. application/pdf
institution Nanyang Technological University
building NTU Library
country Singapore
collection DR-NTU
language English
topic DRNTU::Science::Geology::Volcanoes and earthquakes
spellingShingle DRNTU::Science::Geology::Volcanoes and earthquakes
Hubbard, Judith
Shaw, John H.
Dolan, James
Pratt, Thomas L.
McAuliffe, Lee
Rockwell, Thomas K.
Structure and seismic hazard of the ventura avenue anticline and ventura fault, California : prospect for large, multisegment ruptures in the western transverse ranges
description The Ventura Avenue anticline is one of the fastest uplifting structures in southern California, rising at ∼5  mm/yr. We use well data and seismic reflection profiles to show that the anticline is underlain by the Ventura fault, which extends to seismogenic depth. Fault offset increases with depth, implying that the Ventura Avenue anticline is a fault‐propagation fold. A decrease in the uplift rate since ∼30±10  ka is consistent with the Ventura fault breaking through to the surface at that time and implies that the fault has a recent dip‐slip rate of ∼4.4–6.9  mm/yr. To the west, the Ventura fault and fold trend continues offshore as the Pitas Point fault and its associated hanging wall anticline. The Ventura–Pitas Point fault appears to flatten at about 7.5 km depth to a detachment, called the Sisar decollement, then step down on a blind thrust fault to the north. Other regional faults, including the San Cayetano and Red Mountain faults, link with this system at depth. We suggest that below 7.5 km, these faults may form a nearly continuous surface, posing the threat of large, multisegment earthquakes. Holocene marine terraces on the Ventura Avenue anticline suggest that it grows in discrete events with 5–10 m of uplift, with the latest event having occurred ∼800 years ago (Rockwell, 2011). Uplift this large would require large earthquakes (Mw 7.7–8.1) involving the entire Ventura/Pitas Point system and possibly more structures along strike, such as the San Cayetano fault. Because of the local geography and geology, such events would be associated with significant ground shaking amplification and regional tsunamis.
author2 Earth Observatory of Singapore
author_facet Earth Observatory of Singapore
Hubbard, Judith
Shaw, John H.
Dolan, James
Pratt, Thomas L.
McAuliffe, Lee
Rockwell, Thomas K.
format Article
author Hubbard, Judith
Shaw, John H.
Dolan, James
Pratt, Thomas L.
McAuliffe, Lee
Rockwell, Thomas K.
author_sort Hubbard, Judith
title Structure and seismic hazard of the ventura avenue anticline and ventura fault, California : prospect for large, multisegment ruptures in the western transverse ranges
title_short Structure and seismic hazard of the ventura avenue anticline and ventura fault, California : prospect for large, multisegment ruptures in the western transverse ranges
title_full Structure and seismic hazard of the ventura avenue anticline and ventura fault, California : prospect for large, multisegment ruptures in the western transverse ranges
title_fullStr Structure and seismic hazard of the ventura avenue anticline and ventura fault, California : prospect for large, multisegment ruptures in the western transverse ranges
title_full_unstemmed Structure and seismic hazard of the ventura avenue anticline and ventura fault, California : prospect for large, multisegment ruptures in the western transverse ranges
title_sort structure and seismic hazard of the ventura avenue anticline and ventura fault, california : prospect for large, multisegment ruptures in the western transverse ranges
publishDate 2014
url https://hdl.handle.net/10356/104839
http://hdl.handle.net/10220/20351
_version_ 1681058664342880256