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SCEC Cajon Pass Earthquake Gate Area Initiative: Integrated Science Workshop and Field Trip


Applications Due: August 3, 2018
Participants: 60 or less

Date: September 8-9, 2018
Location: Hilton Palm Springs Resort

SCEC Award: 18203

CONVENERS: Julian Lozos (CSUN), Nate Onderdonk (CSULB), and Craig Nicholson (UCSB)

SUMMARY: SCEC has designated Cajon Pass as the initial area for focused research on the behavior of “Earthquake Gates” (https://www.scec.org/research/ega). Earthquake Gates are areas along a fault or within a fault system, often at major fault intersections, where some ruptures have stopped, while others have passed through. The primary science questions for Earthquake Gates include:

  1. How do fault intersections affect the probability of through-going earthquake ruptures?
  2. How do 3D fault geometry and stress variations modulate these through-going rupture probabilities?
  3. How do prior ruptures affect future rupture paths and probabilities?
  4. Does the current stress field reflect recent rupture history or is it more influenced by other factors?

We will hold a field trip and workshop to bring together researchers from various fields of earthquake science to present recent results pertaining to the Cajon Pass Earthquake Gate, and to determine future research directions. The field trip on Saturday, Sept. 8 will include multiple stops in and around the Cajon Pass region. Following the field trip, we will hold a half-day workshop on Sunday where new advances will be presented and future research directions will be explored for the Cajon Pass as an earthquake gate. We encourage anyone currently working on, or interested in the questions outlined above to apply. We welcome expertise in earthquake geology, seismology, modeling, and the Cajon Pass region. The Sunday presentations and discussion session will be open to as many people as possible, but because of logistical constraints, the field trip will be limited to 35 participants. Participants will be selected based on the level and relevance of their research interests in Cajon Pass and the Cajon Pass EGA Initiative.

Presentation slides may be downloaded by clicking the title of the presentation. PLEASE NOTE: Files are the author’s property. They may contain unpublished or preliminary information and should only be used while viewing the talk.

Saturday, September 8, 2018 (FIELD TRIP)

07:45 - 08:00 Field Trip Check-In (will depart from Hilton Lobby by 08:00)  
09:00 Pick-up participants at optional meeting point in Fontana  
10:00 Stop 1: Lost Lake/Lost Swamp - San Andreas fault
Key slip-rate site for the San Andreas fault (Weldon and Sieh, 1985). Discuss changes in slip rate and rupture history north and south of the pass.
Ray Weldon / Kate Scharer / Sally McGill
11:30 Stop 2: Glen Helen Park
Overview stop where we can see the San Jacinto and San Andreas approaching each other. Discuss if and how coseismic slip transfer occurs, 3D structure of the area, possible transfer structures, rupture models.
Nate Onderdonk / Julian Lozos / Craig Nicholson
12:30 Break for Lunch (bag lunches will be provided)  
14:00 Stop 3: Texas HIll- Lytle Creek Fault
Observe Lytle Creek fault offsets, terrace deposits, discuss strands of the northernmost San Jacinto fault.
Paula FigueiredoRay Weldon
16:00 Stop 4: Day Canyon Fan- Cucamonga fault
Observe Cucamonga fault offsets. Discuss interaction of Transverse Ranges reverse faults with the strike-slip faults.
Devin McPhillips / Nicolas Barth / Kate Scharer
17:00 Field Trip Ends (stop at Fontana meeting point and back at Hilton Lobby by 18:30)  

Sunday, September 9, 2018 (WORKSHOP)

  Session 1: Focus Talks  
13:00 - 13:15 Introduction to earthquake gates Mike Oskin
13:15 - 13:30 Field trip recap and important issues of Cajon Pass geology Nate Onderdonk
13:30 - 13:45 Paleoearthquakes within 100 km and 1000 years of modern Cajon Pass, California Kate Scharer
13:45 - 14:00 Aspects of structures and processes in the Cajon Pass region Yehuda Ben-Zion
14:00 - 14:15 Rupture dynamics and Cajon Pass Julian Lozos
14:15 - 14:30 Multi-cycle strain and stress and implications for the Cajon Pass gate Bridget Smith-Konter
14:30 - 15:00 Discussion of remaining things about the field trip, and any questions and points pertaining to the background information just presented. All
15:00 - 15:20 Break  
  Session 2: Lightning talks   
15:20 - 15:25 Complex CFM 3D Fault Geometry in the Cajon Pass EGA -- More questions than answers (PDF, 571KB) Craig Nicholson
15:25 - 15:30 Speculations on the subsurface geometries of major faults in the Cajon Pass area (PDF, 1.3MB) Jim Evans
15:30 - 15:35 When Do San Andreas Fault Ruptures Diverge On the Other Faults? Gordon Seitz
15:35 - 15:40 Chronology of terraces in the Cajon Pass area and implications for refined slip Paula Figueiredo
15:40 - 15:45 Slip rate of the San Bernardino strand of the San Andreas fault: Results from Badger Canyon and Plunge Creek (PDF, 2MB) Sally McGill
15:45 - 15:50 Update on the BASIN Project: Structure of the San Bernardino Basin Rob Clayton
15:50 - 15:55 Off-fault focal mechanisms not representative of interseismic fault loading suggest deep creep on the northern San Jacinto fault Michele Cooke
15:55 - 16:00 Detangling elastic and plastic deformation through the Cajon Pass Kaj Johnson
16:00 - 16:05 Variations of stress parameters near Cajon Pass from inversion of focal mechanisms (PDF, 3.6MB) Niloufar Abolfathian
16:05 - 16:10 Deep fault bimaterial interfaces around Cajon Pass and their implications for large earthquake ruptures (PDF, 2.3MB) Pieter-Ewald Share
16:10 - 16:15 Probabilities of Multi-fault Ruptures in the Cajon Pass Region from RSQSim (PDF, 887KB) Jacqui Gilchrist
16:15 - 16:20 Testing fault rupture and ground motion models for the Cajon Pass Earthquake Gate Area with precariously balanced rocks (PBRs) Dylan Rood
16:20 - 17:00 Questions about lightning talks. Discussion of current work, things we hope to get from it, how it fits the objectives, what we’d still like to see. More plans for moving forward.  
17:00 Workshop Adjourns  



This workshop is held prior to the 2018 SCEC Annual Meeting.