Re-Estimated Effects of Deep Episodic Slip on the Occurrence and Probability of Great Earthquakes in Cascadia

Abstract

Research Article| November 26, 2013 Re‐Estimated Effects of Deep Episodic Slip on the Occurrence and Probability of Great Earthquakes in Cascadia N. M. Beeler; N. M. Beeler U.S. Geological Survey, Cascades Observatory, 1300 Cardinal Court, Bldg. 10 Suite 100, Vancouver, Washington 98683 Search for other works by this author on: GSW Google Scholar Evelyn Roeloffs; Evelyn Roeloffs U.S. Geological Survey, Cascades Observatory, 1300 Cardinal Court, Bldg. 10 Suite 100, Vancouver, Washington 98683 Search for other works by this author on: GSW Google Scholar Wendy McCausland Wendy McCausland U.S. Geological Survey, Cascades Observatory, 1300 Cardinal Court, Bldg. 10 Suite 100, Vancouver, Washington 98683 Search for other works by this author on: GSW Google Scholar Author and Article Information N. M. Beeler U.S. Geological Survey, Cascades Observatory, 1300 Cardinal Court, Bldg. 10 Suite 100, Vancouver, Washington 98683 Evelyn Roeloffs U.S. Geological Survey, Cascades Observatory, 1300 Cardinal Court, Bldg. 10 Suite 100, Vancouver, Washington 98683 Wendy McCausland U.S. Geological Survey, Cascades Observatory, 1300 Cardinal Court, Bldg. 10 Suite 100, Vancouver, Washington 98683 Publisher: Seismological Society of America First Online: 14 Jul 2017 Online ISSN: 1943-3573 Print ISSN: 0037-1106 Bulletin of the Seismological Society of America (2014) 104 (1): 128–144. https://doi.org/10.1785/0120120022 Article history First Online: 14 Jul 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation N. M. Beeler, Evelyn Roeloffs, Wendy McCausland; Re‐Estimated Effects of Deep Episodic Slip on the Occurrence and Probability of Great Earthquakes in Cascadia. Bulletin of the Seismological Society of America 2013;; 104 (1): 128–144. doi: https://doi.org/10.1785/0120120022 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyBulletin of the Seismological Society of America Search Advanced Search Abstract Mazzotti and Adams (2004) estimated that rapid deep slip during typically two week long episodes beneath northern Washington and southern British Columbia increases the probability of a great Cascadia earthquake by 30–100 times relative to the probability during the ∼58 weeks between slip events. Because the corresponding absolute probability remains very low at ∼0.03% per week, their conclusion is that though it is more likely that a great earthquake will occur during a rapid slip event than during other times, a great earthquake is unlikely to occur during any particular rapid slip event. This previous estimate used a failure model in which great earthquakes initiate instantaneously at a stress threshold. We refine the estimate, assuming a delayed failure model that is based on laboratory‐observed earthquake initiation. Laboratory tests show that failure of intact rock in shear and the onset of rapid slip on pre‐existing faults do not occur at a threshold stress. Instead, slip onset is gradual and shows a damped response to stress and loading rate changes. The characteristic time of failure depends on loading rate and effective normal stress. Using this model, the probability enhancement during the period of rapid slip in Cascadia is negligible (<10%) for effective normal stresses of 10 MPa or more and only increases by 1.5 times for an effective normal stress of 1 MPa. We present arguments that the hypocentral effective normal stress exceeds 1 MPa. In addition, the probability enhancement due to rapid slip extends into the interevent period. With this delayed failure model for effective normal stresses greater than or equal to 50 kPa, it is more likely that a great earthquake will occur between the periods of rapid deep slip than during them. Our conclusion is that great earthquake occurrence is not significantly enhanced by episodic deep slip events. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.