Wednesday, October 5, 2016

Goodbye to SoSAFE (Southern San Andreas Fault Evaluation): review and a recent workshop

The SoSAFE activity was a very successful data gathering and interdisciplinary science rallying activity in the Southern California Earthquake Center (SCEC) for 10 years. Its early leader was Dr. Ken Hudnut from the USGS. The original aspiration was to develop understanding of the last 2000 years of activity along the Southern San Andreas Fault. I was fortunate to be invited to help co lead SoSAFE in 2011. Dr. Kate Scharer (USGS) was the other co-leader. Her recent research has been largely focused on understanding the southern San Andreas Fault paleoseismic history. I very much appreciated the chance to work with Kate to help coordinate the research activity of SoSAFE withing SCEC as part of its Planning Committee. Our main efforts included evaluating proposals and helping coordinate and promote the research of our colleagues. We did a few additional activities including the "FieldShop" in which we made a group field trip to discuss and assess small offset landforms along the San Andreas Fault Mojave segment near Pearblossom. The outcome of the FieldShop was a paper lead by Kate: Scharer, K. M., Salisbury, J. B., Arrowsmith, J R., Rockwell, T. K., Southern San Andreas Fault Evaluation field activity: Approaches to measuring small geomorphic offsets and challenges and recommendations for active fault studies, Seismological Research Letters, v. 85, no. 1, ppl 68 - 76, 2014. In addition, we also organized (along with Prof. Mike Oskin from UC Davis) the SoSAFE and Earthquake Geology Geochronology workshop in 2014. The discussions of novel applications of geochronology for earthquake geology were really interesting and helpful for the community. SoSAFE has been sunsetted as an activity within SCEC as it moves into its 5th iteration (SCEC5). Much of the important work of SoSAFE will be subsumed (and hopefully continued) in the San Andreas Fault System Working Group to be led by Kate and Prof. Michele Cooke (UMass). It makes some sense I suppose as a refresh on SCEC structure, but I and others are concerned about the loss of emphasis on paleoseismic data gathering.

Nice cover image produced by Barrett Salisbury (ASU).

In our last SoSAFE activity, Kate and I organized a workshop for Sept. 10, 2016: SCEC SoSAFE Workshop: Recent Successes and Future Challenges. The workshop had 3 main themes:

  1. Earthquake recurrence and slip over short and long term: how does it all add up?
  2. Integrating earthquake and paleoclimate/paleoenvironmental chronologies on the SoSAFE System
  3. Outside looking in: Broad applications of Behavior of high slip rate faults
The workshop was well attended (we capped it at 40 people, but many more wanted to join).

Several synthesis points were evident from the presentations and discussions:

  • The opportunity to and importance of documenting the full spectrum of slip behavior at a range of slip speeds (creep to seismic) and both on and off fault. Where in space and time along and adjacent to the fault surface is there deformation, and how might the behavior vary over time? How to capture the integrated effect of fine scale fracturing? (Toké, Milliner, Lindsey)
  • Variable slip at a point in successive earthquakes is suggested by detailed evidence from many sites. In some paleoseismic records, we may be seeing both small and large events mixed in the same record. This is a good picture of the earthquake phenomena but a greater challenge for interpretation. (Dawson, Salisbury, Rockwell, Biasi)
  • Paleoseismic event recognition and resolveability. Are we under or over counting paleo earthquakes? The consensus among the group (and as analyzed by Biasi) was that both happen and so suggestions of systematic overcounting (e.g., D. Jackson) were not supported by experience. But, there certainly is value in exploring ways to systematize paleoseismic data (evidence, age control, correlation, etc.). (Dawson, Rockwell, Biasi, Milner). Tim Dawson reminded us of the important work of Bonilla and Lienkamper, 1991. The time scale during which many of the comparisons are being made (~1000 yrs) may be too short to completely assess the question of moment rate fluctuation across the SoSAFE system.
  • Slip rates vary in space and time probably as a function of evolving fault geometry (at multiple length scales) and mechanical interaction (Cooke, Onderdonk).
  • Interpreting offset per event from the reconstruction of fine scale landforms remains challenging. 3D excavation and reconstruction is desired but time consuming (and itself can have subtleties and ambiguities). There is a "... tension between collection of observations at as many locations as possible (assuming there will be signal in the noise [Large N]) versus inclusion of only data that are clearly offsets (rather than deflections) and have good quality ranking." (Scharer, et al. 2014). Interpretation of small geomorphic offsets will not go away given its convenience, the availability of high resolution imagery and topography, and the potential to assess remote structures. But, we must continue to validate and push to understand what we are measuring, entertain alternatives, identify 3D anchor sites, etc. (Salisbury)
  • Earthquake simulators are moving forward as the preferred integrative tool for forecasting earthquake behavior across the SAF system ("Paleoearthquake data and slip rates battle it out in UCERF3--RSQSIM to the rescue"--Kevin Milner, USC). Jaqui Gilchrist (USC) gave a nice presentation reviewing the simulator approach. Her faults are quite smooth from the perspective of the many geologists in the room. Importantly, we learned about the tuning that is done by adjusting fault normal stresses to match paleoearthquake rates across the system. She showed that there is a gap between the curated paleoearthquake datasets she has used and the data producers. There is a need for deeper access to paleoearthquake data and metadata. SCEC-VDO was rebuilt in 2016 and is a valuable tool for visualization and exploration.
  • Field earthquake geology is time and resource consuming. Assuming that the site conditions are good enough to preserve a high quality record, it is important to recognize that it takes at lot to produce high quality field studies, both in the field, as well as in the geochronology laboratory.
The early afternoon featured thought provoking talks about paleoclimate and paleoenvironmental chronologies. Here are a few of my takeaways:
  • Kate showed in her 2014 paper (Scharer, K. et al., 2014b. Paleoearthquakes at Frazier Mountain, California delimit extent and frequency of past San Andreas Fault ruptures along 1857 trace. Geophysical Research Letters, 41(13), pp.4527– 4534.) how using paleosol and sediment accumulation curves would illuminate similarly timed landscape variation in California. She demonstrated that it was likely that earthquakes with overlapping ages at separate paleoseismic sites were different because their evidence was above and below a period of slow sediment accumulation (a paleosol). This is quite exciting and a frontier for earthquake geology. The challenge is what is the best proxy? Paleoprecipitation indicators? or Pollen or fire? How to balance convenience and the ability to measure with environmental sensitivy and ability to date?
  • Prof. Matt Kirby (CSU Fullerton) presented a nice review of paleoclimate and paleoenvironmental proxies (temperature, precipitation, circulation, flooding, fire, other geomorphic disturbance). He focused on the rare lake records of southern California and differentiated millenial, centennial, sub-centenial to decadal, and annual time scales and their different drivers (mostly interactions with the Pacific Ocean). The millenial scale offers an opportunity to look at (synchronous formation of large markers along the SoSAFE System--e.g., Wallace Creek at 3,700 years BP and other similarly aged offset landforms). The sub-centennial to decadal (or finer scales) offer the opportunity for further differentiation of paleoearthquakes (e.g., Scharer, et al., 2014b) as well as the formation of small scale markers for single or few event offsets.
  • Matt called out the need for common protocols, the value of looking at sections together, and that there were lots of interesting possible sites out there. We can use existing sites as benchmarks and prospect for new ones. This work costs $$!
  • Prof. Nick McKay (NAU) offered valuable perspective as well as a potential path forward for organizing paleoseismic and paleoclimate data. He talked about the PAGES2K effort as a distributed global collaboration on past climate. It relies on a cyberinfrastructure of linked paleodata (McKay, N., and Emile-Geay, J., 2015, Technical Note: The linked paleo data framework – a common tongue for paleoclimatology, Climate of the Past, 11, 4309-4327.). He ended with some commentary on the challenges of supporting such a data effort (1) Identify metadata, 2) Structure metadata hierachically, 3) Be thoughtful about Selection Criteria, 4) Iterative data and metadata assimilation, and 5) Flexible scientific control).

Many thanks to our colleagues for their great ideas and community spirit in support of SoSAFE. Adieu!!

Saturday, October 1, 2016


Nancy Glenn (Boise State) led a training workshop with Chris Crosby (UNAVCO), Tristan Goulden & Shelley Petroy (NEON), and me this last week on topographic, geomorphic, and vegetation analysis with lidar. We emphasized the NEON project and its substantial Airborne Observation Platform with its lidar scanners. Tristan is the Remote Sensing Specialist with lidar expertise for NEON and in charge of those acquisitions. Shelley is the data products lead for all of NEON. It was quite interesting to learn more about NEON and also to see the interesting interdisciplinary opportunities for research. The participants came from a range of backgrounds and were a pleasure to meet and work with.

Shelley Petroy and Chris Crosby sharing their knowledge with the group

The workshop web site has some good lecture and exercise/tutorial content (look towards the bottom at the "Workshop Material" link. I built some simple videos (look for playlists on NEON Points to Raster and NEON OpenTopography, Topographic Metrics and Drainage Network) demonstrating some aspects of the tutorials. At OpenTopography, we have started to distribute NEON lidar data (NEON D17 Pacific Southwest- California).

We had a great time in Boise. The classroom was excellent and Nancy was kind to schedule a civilized stop time in the afternoon so there was time for a run before the pleasant evening receptions. Below is a picture from above Boise:

An interesting coincidence was that at the same time as our workshop and in Boise was the Subduction Zone Observatory Workshop. I could imagine having been at that meeting too!

Introduction to Structure from Motion (SfM) Photogrammetry for Earth Science Research and Education short course (Sept. 24, 2016 at the GSA meeting)

Chris Crosby (UNAVCO), Ed Nissen (Colorado School of Mines), and I recently ran a one day short course at the Geological Society of America Meeting on an Introduction to Structure from Motion (SfM) Photogrammetry for Earth Science Research and Education. We had a good time sharing our enthusiasm for Structure from Motion with the group of 25 or so enthusastic participants. They came from a range of backgrounds as educators as well as researchers in active faulting, geomorphology, sedimentary geology, engineering, and more.

The course web site has some very useful content lectures and exercises. And, Chris reminded us of some quite helpful SfM docmentation that he and Katherine Shervais put together:

The workshop was co-sponsored by UNAVCO as well as OpenTopography. At OpenTopography, we are staring to provide SfM data and are working to build a drag and drop capability for user contributed correctly documented SfM datasets.

Ed Nissen giving the Introduction to Structure from Motion

Saturday, April 2, 2016

COMET Topography Workshop 31/3/2016 – 1/4/2016

The COMET Topography workshop just completed (31/3/2016 – 1/4/2016) with great success. It was hosted by the Oxford University Earth Sciences and ably lead by Austin Elliott (also active here: @TTremblingEarth). John Elliott, David Mackenzie, and Zhou Yu made important contributions. Professors Barry Parsons and Rich Walker provided oversight. I had a great time helping out with the workshop. It was great fun to share our enthusiasm for high resolution topography and to represent and present OpenTopography to the esteemed group of mostly earthquake faulting and volcano scientists.

The workshop emphasized topography produced from photogrammetric methods. The first emphasis was on more traditional photogrammetry applied to relatively high resolution space-based bi- or tri-stereo imaging (e.g., SPOT and Pleiades). The software of choice was ERDAS Imagine with its Photogrammetry Suite. I enjoyed learning more about this technology and these data which the Oxford team among others has been using with great success for characterizing active faulting.The second emphasis was on Structure from Motion--something I have some more experience with. It was great to see the strong interest and burgeoning expertise among the various participants as they apply this methodology with ground and UAV-based images to a range of faulting and volcanic problems. The OpenTopography workshops over the last couple of years have featured SfM as well (with great contributions from Ed Nissen). I got a good primer on georeferencing and networked SfM.

The workshop agenda is here: link.

See also this nice blog post about the workshop: link.

The group photo. Sunny moment in Oxford; lots of great scientific power here and a fun lot too! Photo by David Sandwell (Oxford University).

Introductory science motivations: "Sharpening our view of earth processes with high resolution topography". Photo by David Sandwell (Oxford University).

Sunday, January 31, 2016

Short Course just completed: Imaging and Analyzing Southern California's Active Faults with High Resolution Topography

We just completed our most recent OpenTopography short course: Imaging and Analyzing Southern California's Active Faults with High Resolution Topography. The course was sponsored by The Southern California Earthquake Center, UNAVCO, EarthScope, and OpenTopography. It was a pleasure to work again Chris Crosby and Ed Nissen and many thanks to Alana Williams (along with Jessica Sutton, Barrett Salisbury, and Gayatri Marliyani) for the local logistical support.

Nice montage put together by Barrett Salisbury for the course advertisement.

We had 90 applications for just 34 slots, so we emphasized early career scientists (mostly graduate students), and research in Southern California given SCEC's sponsorship. We hope to run another course soon (April 2016?) to catch up a bit more with the demand. It was wonderful to meet new people and share our enthusiasm for high resolution topography!

Students hard at work in the computer lab--Ed Nissen at the controls.

New: We recorded some of the talks. I made a summary playlist of my talk as a test. The audio is not great, but it is a summary motivation for the meeting: Sharpening our view of earth processes with high resolution topography

Summary write up for EarthScope newsletter but of relevance here too:

High resolution topographic data has become an important tool for earthquake scientists to make detailed observations and model surface evolution. Within the last decade, several efforts have been made to collect high resolution topographic (HRT) data for active faults (e.g. The B4 project, EarthScope, and numerous National Center for Airborne Laser Mapping--NCALM and USGS projects). These datasets are freely available online through OpenTopography, a NSF funded data distribution portal. The active faulting community has taken great interest in these exciting datasets, using them to generate new and important insights into earthquake processes in Southern California and elsewhere.

The EarthScope program supported the acquisition of several thousand square km of high resolution topography from lidar along active faults of the western US. The target areas included Northern, Southern & Eastern California (everything not already covered by the B4 project along the San Jacinto fault and southern San Andreas Fault; Prentice, et al., 2009), Yakima (Washington), Alaska (portions of the Denali rupture and Totschunda fault--see figure), and the Intermountain Seismic Belt (portions of the Wasatch Fault and Yellowstone). These data have been invaluable for studying deformation processes in a complementary mode to the fault zone drilling, geodetic, and seismological observatories of EarthScope.

Prentice, C. S., Crosby, C. J., Whitehill, C. S., Arrowsmith, J R., Furlong, K. P., Phillips, D. A., GeoEarthScope LiDAR illuminates northern California's active faults, EOS Transactions of the American Geophysical Union, v. 90, no. 7, p. 55, 2009.

Monday, November 2, 2015

Links and commentary on earthquakes 11 km NE of Black Canyon City, Arizona (~11:30 pm local time; November 1, 2015)

At least 3 earthquakes (M3.2, M4.1, M4.0) occurred last night 11 km NE of Black Canyon City, Arizona (I am sorry to have missed being at a NASA meeting in Washington D.C.!). It was widely felt across central Arizona including greater Phoenix (USGS' Did You Feel Ithas >4800 responses by 3:30 am). USGS estimates 4.6M people were exposed to weak shaking.

The sequence began with a M3.2 at 8:59 pm (foreshock). The M4.1 mainshock occurred at 11:29 pm within 2 km of the foreshock. 20 minutes later and 4.6 km SSW the M4.0 aftershock occurred. An M3.1 event occurred in the area Fri May 08 2009. There are no mapped active faults nearby but the roughly north-south orientation is consistent with the bedrock geologic structure in the area and note the mapped active faults to the east (Horseshoe, Carefree, and Sugarloaf--all similar orientation

PDF of above map

Seismogram recorded at ASU processed by John D. West. PDF of above

Seismograms recorded at ASU processed by John D. West. PDF of above

There is a very cool large landslide near to Black Canyon City (see this post), but the earthquakes and landslides are not associated. I would think that the slide was shaken enough to move, and certainly the steep slopes of the region should have produced some rockfalls and other mass movements from this earthquake sequence.

Here are some links for the event:

Here are some links for background on Arizona earthquakes: