I gave it a try. My dissertation was entitled "Coupled Tectonic Deformation and Geomorphic Degradation along the San Andreas Fault System". I tried that as well as a shorter version "Tectonic Geomorphic San Andreas Fault" with a couple of different styles. I have to ponder the results. Some of the other examples work well when there is an object more recognizeable (such as a bird or T-cell), or somehow I need to give it a more interesting prompt. But the results are interesting. I like the trading card format.
Sunday, December 5, 2021
Wednesday, December 1, 2021
I recently wrote this memorial for the Geological Society of America Structural Geology and Tectonics Division (which I am now beginning my stint as chairman or soon will). That is the reason for the first person plural.
We heard with great sadness and shock of the passing of our dear friend and colleague Professor Paul J. Umhoefer (Northern Arizona University) in late November 2021. Some of us saw him at the 2021 GSA meeting and to lose him so soon after weighs on us.
Paul Umhoefer was a great scientist, mentor and teacher, and servant to his professional community and department. He was well known for his research in tectonics, basin analysis, structural geology with carefully collected field data from the western US, Baja California, and Anatolia.
Much of his research was done in close collaboration with his many students at NAU. He was a strong mentor who guided many of those projects to publication and the students went on to success, especially in academia and the petroleum and geo-environmental industries. His professional colleagues appreciated his guidance and invitation to join interesting projects.
Paul was a tireless leader in the geoscience community. He helped to propel important community initiatives, including Margins/GeoPrisms. He not only contributed synthetic ideas but was an integrator and conciliator. He was an effective chair of his department helping guide it in a time of important growth. We are grateful for this leadership in the Geological Society of America Structural Geology and Tectonics Division where he was a long time active member, proponent of GSA fellows, and had recently completed the arc of leadership of the division.
Along with his tireless work ethic, Paul was enthusiastic and gregarious with a big smile and a joke for his friends and colleagues delivered in his deep creaky voice. He loved to talk about ideas: geoscience, politics, sports.
We counted on seeing him again soon. We are sorry to lose him and our thoughts are with his family and close friends.
--Ramon Arrowsmith (incoming Division Chair) on behalf of the Geological Society of America Structural Geology and Tectonics Division
Sunday, October 24, 2021
I heard in late August 2021 that Omar Abdullah was killed in the unrest that is occurring in Ethiopia. I did not learn of any details but he was an embasa--a lion--and no doubt he was there defending his family and lands. He was an amazing guy that I got to know over the years working in the Afar with the Ledi Geraru Project. Others knew him better. I appreciated him very much. He was from the Hadar woreda--administrative area--but we gave him a special title: "camp specialist" so we could keep him employed even when we were working in other areas with other Afars. Even the other Afars grew to appreciate him and his sense of humor.
Omar had a great sense of humor. There is a drainage called "Fat Ha'". It means big mouth in Afar. As Omar said, "like me!" He was also fascinated with our western scientist lives. He called himself "Black American." He was very friendly and happy to solve problems for the success of the project.
We probably will not be back to Ethiopia and the Afar for a while sadly given the unrest. It will be very sad when we do and we really feel the loss of Omar (and probably others of our Afar friends). May he rest in peace. He always wanted me to bring him a small radio I think so he could listen to music while he waited for us to our work. I regret never quite getting around to that.
Friday, June 11, 2021
In April 2021, we finished a fairly intensive project: AC GEO Report on Portfolio Review of EAR Seismology and Geodesy Instrumentation. I defer to that page as the official one, but I wanted to put a note here as well.
I was the chair of the committee, and the citation is
Arrowsmith, J R., Brodsky, E. E., Cooper, C. M., Elliott, J. L., Fee, D., Fischer, K.M., Hammond, W. C., La Femina, P., Lekic, V., Wang, H., and Worthington, L. L., Recommendations for Enabling Earth Science Through NSF’s Geophysical Facility – A Portfolio Review of EAR Seismology and Geodesy Instrumentation, Report to the US National Science Foundation, April 2021.
But, I want to really highlight the efforts of the entire committee! This was a really strong group that worked hard and respectfully together to come up with something we are quite proud of. It has some depth which I hope will give it shelf life.
Here are the rest of the Acknowledgements:
Thank you to UNAVCO President Rebecca Bendick and Director of Geodetic Infrastructure Glen Mattioli as well as IRIS President Robert Woodward and Portable Programs Manager Kent Anderson for their rapid and thorough responses to the committee queries. Christopher Crosby (UNAVCO) provided input on geodetic imaging. Jonathan Ajo-Franklin (Rice University), Kent Anderson (IRIS), Jnaneshwar Das (Arizona State University), Rob Evans (WHOI), W. Steven Holbrook (Virginia Tech), and Glen S. Mattioli (UNAVCO) kindly made themselves available for interviews with the committee. We are grateful to Lindsay M. Martin who supported the committee very ably as science assistant from the National Science Foundation. Finally, many thanks to Margaret Benoit (National Science Foundation Program Director) for her careful guidance.
Wednesday, January 6, 2021
The Salt River in central Arizona has a spectactular set of fluvial terraces developed along it. I have lead a number of field trips along the Salt River for outreach and most importantly for our GLG451 Field Geology I course where we use a site along the Salt River for a mapping exercise. I have recently updated the materials associated with that exercise in anticipation of this Spring's class which will include a virtual component.
I built on some of the very nice writing and descriptions of Professor Pewe when I wrote up a field trip guide and ran a few field trips in the early 2000s. See this LINK. I updated that guide and it is available here: Landscape and geologic history along the Salt River near Tempe and Mesa, Arizona.
Here is the assignment with many additional links and explanations: Virtual Field Geology assignment for Salt River Field Geology I 2021.
I made a long explanation of the GIS:
These were of great interest to Professor Troy L. Pewe of Arizona State University's Department of Geology. He moved to Arizona from Alaska and converted his research from permafrost to desert processes. I was lucky to learn from him when I first came to ASU in 1995. He took me under his wing and shared with me much of what he had learned. Most importantly, he helped me to learn the field trips and field sites he had developed and discovered. I am extremely grateful to him. I recognize Brian Gootee who was a great friend of the Pewe Family and who has preserved much of the Pewe legacy at the Arizona Geological Survey.
Pictures from those early field trips with Prof. Pewe.
Thursday, December 31, 2020
I became obsessed with diffusion erosion modeling in my PhD work. It is a simple (certainly oversimplified) way to think about how hillsloopes may change over time in the absence of mass wasting, debris flow, and fluvial processes. There is a lot to say about it, but I wanted to capture a few items I recently developed.
One of the challenges that I have had in some applications is that the computational "space" was too small in the spreadsheet, given that it is fixed. Of course this is not a problem if one dynamically determines the number of time steps for example based on a stability criterion and you do it with a for or while loop in something like Matlab. So, when I was helping Emily Apel with her senior thesis recently, I built her a big spreadsheet (seemed easier given the limited time that she had.
Here is the original spreadsheet with only 27 space steps and 191 time steps. It is good for teaching and quick demos: LINK to Spreadsheet.
Here is the big spreadsheet with 250 space steps and 1000 time steps: LINK.
And, here is a video that I built to explain the general activity for Emily Apel, but it may be useful for others. It explains the two spreadsheets that are linked above.
One of the cirtical concepts that is accessible in both of these spreadsheets is the opportunity explore not only initial step models, but also continuously displaced scenarios.
Here are a few other blog posts and recent publications which might be of interest as well:
- One dimensional morphological modeling of transport and production- limited fault scarps
- Updated review of fault scarp analysis
- Exploring the Topographic Evolution of Cinder Cones
- Some of my and my colleague's papers on these topics:
- Arrowsmith, J R. and Rhodes, D. D., Original forms and initial modifications of the Galway Lake Road scarp formed along the Emerson Fault during the 28 June 1992 Landers, California, earthquake, Bulletin of the Seismological Society of America, 84, 511-527, 1994.
- Arrowsmith, J R., Pollard, D. D., and Rhodes, D. D., Hillslope development in areas of active tectonics, Journal of Geophysical Research, 101, B3, 6,255-6,275, 1996. Correction: Journal of Geophysical Research, 104, B1, 805, 1999.
- Arrowsmith, J R., Rhodes, D. D., and Pollard, D. D., Morphologic dating of scarps formed by repeated slip events along the San Andreas Fault, Carrizo Plain, California, Journal of Geophysical Research, 103, B5, 10,141--10,160, 1998.
- Hilley, G. E., Arrowsmith, J R., Amoroso, L., The role of the interaction of normal faults and fractures on scarp morphology, Geophysical Research Letters, 28, p. 3,777-3,780, 2001.
- de Michieli Vitturi, M. and Arrowsmith, J R., Two dimensional nonlinear diffusive numerical simulation of geomorphic modifications to cinder cones, Earth Surface Processes and Landforms, doi:10.1002/esp.3423, 2013.
- Wei Zhanyu, Arrowsmith, J R., He, H., Evaluating fluvial terrace riser degradation using LiDAR-derived topography: An example from the northern Tian Shan, China, Journal of Asian Earth Sciences, Volume 105, Pages 430-442, 2015.
- Xu, J., Arrowsmith, J R, Chen, J., Schoenbohm, L. M., Li, T., Yuan, Z., Evaluating young fluvial terrace riser degradation using a nonlinear transport model: With application to the Kongur Normal Fault in the Pamir, northwest China, Earth Surface Processes and Landforms, DOI: 10.1002/esp.5022, 2020.
Tuesday, December 15, 2020
In my classes and for research, sometimes it is useful to calculate the scalar seismic moment (M0; basically a geometric measure of the total static energy release at a 0th order). It is a function of the area of a fault that slipped times the average slip times the shear modulus of the volume. The latter is usually assumed to be 30GPa. The main challenge (after determining the parameters) is to get the units all to be the same (dimensions of Newtons and meters):
And, once we have that scalar moment in Nm, then we usually want to convert it to moment magnitude (Mw):