Simple computations of scalar seismic moment and moment magnitude

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):

M₀= mu*Length*Width*U_bar.

And, once we have that scalar moment in Nm, then we usually want to convert it to moment magnitude (M_w):

M_w = 2/3 log10(M₀) – 6.

Here is a simple spreadsheet to do this calculation: LINK
Here is a simple and older lecture I have used in introductory level geoscience courses: LINK

Many thanks to Petroleum Experts Limited for 2020 Donation

Petroleum Experts Limited has again provided the School of Earth and Space Exploration with licensed software for 2D and 3D kinematic modelling, geomechanical, fracture, and fault response modeling and fault and stress analyses. These licenses are valued at $2,223,600.00 US Dollars and will enable our faculty and students to build and analyze complex 3D fault models to develop understanding of tectonic processes and to anticipate earthquake hazards.

We have acknowledged this donation in our March 2020 SESE Newsletter (LINK) as well as express our thanks in our building displays:

We are grateful for this donation. The MOVE suite of software is a powerful environment for 3D interpretation. My students and colleagues are using it to build 3D fault models. We will begin to work on sedimentary architecture in extensional environments in the coming year. In addition, with continued support of the licensed software, we will develop course material for it for our geology majors.

Example image from Petroleum Experts/MOVE.

Virtual field geology exercises for GLG451 Field Geology I Spring 2020

Even before the COVID-19 crisis changed everything, I was working this semester to build some virtual options for my Field Geology I (GLG451) course. Two students are physically unable to do the field work, and then another had a crisis and missed two weekend field trips. The course has three weekend field trips and then a mini camp over spring break.

Locations of the field trips.

I decided to try to build some digital versions of the field trips using very high resolution digital elevation models and orthophotos from our SUAS systems (thanks to Tyler Scott for doing the flying and the SfM work). I wanted these to be as similar as possible to what the regular students experience so I give some initial information on the maps as well as numerous pictures from the ground and videos from the sUAS. For most of the exercises in the case of my class, I also am providing rock samples to the students of each of the mapping units.

All of the information for each of the assignments is in a long pdf which has the text assignment, links to data and images, etc. and then some explanation. It also has a topographic profile for a cross section, etc.
I am very happy to share with anyone who might find these useful. Here are the modules and the current status:

Module	Status	Link
Dreamy Draw, Phoenix Mountains, AZ	Done	LINK
Goldfields, Superstition Mountains, AZ	Done	LINK
Salt River, Bush Highway, AZ	Done	LINK
Arnett Creek, AZ	Done	LINK

Example video for the Goldfields in which we fly along the path of the introductory tour:

Here is an example of one of the explanatory tutorial videos for ArcGIS:

Here is geology tour for the Salt River mapping project:

Here is longer geology tour for the Arnett Creek Spring Break mapping project:

Call for research papers: Unveiling Active Faults: Multiscale Perspectives and Alternative Approaches Addressing the Seismic Hazard Challenge

Along with Federica Ferrarini, Nathan Toké, and Michele M. C. Carafa, we are looking forward to submissions to this special "issue" from the Frontiers journal: Unveiling Active Faults: Multiscale Perspectives and Alternative Approaches Addressing the Seismic Hazard Challenge.

Federica made a nice flyer to share: LINK

Central Apennine settled landscape with active normal fault (photograph by Federica Ferrarini).

Despite decades of progress toward mitigating seismic hazard, characterizing the seismic potential of an area remains a complex process. Particularly challenging are seismically active regions characterized by low slip rate faults which can give rise to weak geomorphic expressions when combined with high erosion or sedimentation rates. Similar compounding issues may also manifest in densely populated areas where anthropogenic modifications, or vegetation cover further challenge assessment of fault activity or where structural complications may contribute to multiple interpretations. Noticeable advances in remote sensing technology geodetic measurements and dating Late Quaternary landforms and sediments have moved our understanding forward.

This Frontiers Research Topic welcomes contributions that present examples and approaches which strive to improve our understanding of active faulting processes over diverse geological settings and at broad spatial scales of investigation. We encourage the submission of research papers from a wide range of geoscience disciplines (field geology, structural geology, tectonic geomorphology, paleoseismology, seismology, remote sensing, numerical modeling) and from the scale of a field site to regional scale analyses. We welcome contributions with the main goal to bridge the gap between our observations, fundamental understanding of faulting processes, and effective seismic hazard assessment.

Please think about a contribution! Submit an abstract by January 29, 2020 (not required). The manuscripts are due May 29, 2020.

Many thanks to Petroleum Experts Limited

Petroleum Experts Limited has provided the School of Earth and Space Exploration with licensed software for 2D and 3D kinematic modelling, geomechanical, fracture, and fault response modeling and fault and stress analyses. These licenses are valued at $2.18M and will enable our faculty and students to build and analyze complex 3D fault models to develop understanding of tectonic processes and to anticipate earthquake hazards.

Here is a LINK to our SESE newsletter acknowledging the donation as well

We are really grateful for this donation. The MOVE suite of software is a powerful environment for 3D interpretation. My students and colleagues are using it to build 3D fault models. We hope to begin to work on sedimentary architecture in extensional environments in the coming year. In addition, with continued support of the licensed software, we will develop course material for it for our geology majors.

Example image from Petroleum Experts/MOVE.

Remembering Donal M. Ragan

Professor Emeritus of Geology Donal M. Ragan passed away in February 2019. Unfortunately, I had lost some contact with him in the last years. However, I was first hired on in 1995 at ASU to take Don's position (from which he had retired) and teach Structural Geology. He was still active, working on his book and so he came by often to talk with me and my students (especially George Hilley). Don and his wife Janne were also kind to have me over for dinner occasionally. They were very generous. This memory of Don is incomplete, but I wanted to capture a few thoughts and recollections.

This is the only picture I could find of Don. He is there on the left (along with Lee Amoroso, Jeri J. Young, and George Hilley) during a field trip to the Carrizo Plain in the late 1990s.

I don't have all of Don's biography. I recall he was born in southern California and maybe went to Occidental College. He was in the Army and talked about the discipline and repetitiveness of learning how to dissassemble and assemble a machine gun. He went to the University of Washington where he worked on deformation in the Twin Sisters Dunite. He was at Imperial College where he worked with John Ramsay. He moved to the University of Alaska (UAF) and published on deformation associated with glacial ice (e.g., Ragan, 1969). He moved to Arizona State University in 1965 at the behest of Prof. T. L. Péwé who had been hired to be chairman and who knew Don from UAF.

We worked a fair bit with Don on MATLAB implementations of his exercises and ideas. A couple are here. And, he was an avid LaTEX user having had problems in the 3rd Edition of the book when he did not have good control over the copy editing and production. He taught us about dashes and quotes.

In 2000, Don taught a series of lectures on Structural Geology. I helped a bit mostly as coordinator and provider of moral support. These reflected the development for the book and all I really have are the handouts and figures for transparencies and a few notes:

• Introduction
• Lecture 1--Introduction and mostly vectors
• Lecture 2--Force and stress
• Lecture 3--Faulting
• Arrowsmith notes on Force, stress, and faulting
• Lecture 4--Deformation I
• Lecture 5--Deformation II
• Lecture 6--Deformation III
• Lecture 7--Flow
• Pfiffner and Ramsay, 1982, Constraints on geological strain rates: arguments from finite strain states of naturally deformed rocks, Journal of Geophysical Research

Don was outspoken about quantitative approaches in structural geology: "Despite all this effort one can still find in professional articles statements that violate basic laws of physics and in some current textbooks there are important omissions, misstatements, misinterpretations and errors when dealing with structure making processes." (from his review of The Life of Frank Coles Phillips).

I worked with him for a while on the 4th edition of the textbook, but did not contribute enough in time to stay a coauthor. Nevertheless, I learned so much from Don and did what I could to apply those lessons in the GLG310 Structural Geology and the GLG510 Advanced Structural Geology courses. We talked often about how to teach structural geology and how to bring more quantification and precision to it. We followed the developments of the structural geology textbook (FSG) of Professor David Pollard at Stanford. Don and I wrote a short review of an early version of a manuscript on kinematics and mechanics here. Don wrote a blurb for the book: "This is the best book on structural geology in a long time. It is both rooted in classical mechanics and visionary. In their characteristic fashion, Pollard and Fletcher lay out the physical concepts and tools needed to understand the structure-making processes and give many examples of their use. If you have any interest at all in the subject read this book, but be prepared to work. You’ll be glad you did."

Viewing 3D planes (discs) with a specified diameter and orientation in ArcScene

We have been pondering how to visualize planes in 3D as a way to assess correlation of beds in an area. My colleague Chris Campisano and our jointly supervised PhD student Dominique Garello was asking about this for a while. We discussed a few solutions, including the MOVE suite and RIMS among others. I know there is a lot of software out there for this.

I decided to tackle it in a very simple way with the constraint that it would only use Excel and ArcGIS (ArcMap and ArcScene). I googled around an there was not an obvious solution already.

The basic steps:

1. Produce a disc in MS Excel by creating a circle with a specified diameter and center. Rotate the dip around N-S axis and then rotate around vertical to apply the strike (then make it the correct size and translate to correct center)
2. Load the rim points into ArcMap, view the X Y points with elevations
3. Create a TIN (triangulate the rim points to make the disk)
4. Visualize it in ArcScene

I wrote a tutorial (link) and the spreadsheet is here.

Mapping landforms with applications to geomorphology and earthquake geology EXERCISE

I wanted to share a project I have developed on and off for about 10 years. It is a classroom exercise for Mapping landforms with applications to geomorphology and earthquake geology. So far, it has an example for strike-slip faults (Wallace Creek along the San Andreas Fault), and blind thrust faults (Wheeler Ridge in Southern California). I have an intention to add a normal fault example but have not finished it yet.

The basic idea is that the exercises could be done "analog"--that is on paper in a classroom. They emphasize some simple morphologic and geomorphic mapping (but on high resolution topography base maps from lidar data collected by NCALM and available for download from OpenTopography), and then provide landform ages so that students can calculate slip rate or surface uplift rates. I am not sure they are so well explained so any feed back is welcome.

Exercise material:

• 2016 Mapping landforms with applications to geomorphology and earthquake geology EXERCISE pdf
• Supplemental material (for instructors)
• Wallace Creek--uses B4 lidar data
• Papers:
  
  • Wallace, R. E. (1968). Notes on stream channels offset by the San Andreas fault, southern Coast Ranges, California. In Conference on Geologic Problems of the San Andreas Fault System. Stanford University Publication in Geological Sciences (Vol. 11, pp. 6-21).
  • Sieh, K. E., & Jahns, R. H. (1984). Holocene activity of the San Andreas Fault at Wallace Creek, California. Geological Society of America Bulletin, 95, 883–896.
  • Sieh, K. E., & Wallace, R. E. (1987). The San Andreas Fault at Wallace Creek, San Luis Obispo County, California. In Geological Society of America Centennial Field Guide -- Cordilleran Section (pp. 233–238).
• Demonstrative presentation (ppt) and (pdf) and video flyover
• Pictures of the board from demonstration at U. Potsdam, 2019.
• Wheeler Ridge--uses NCALM student seed grant lidar data
• Papers:
  • Medwedeff, D. A. (1992). Geometry and kinematics of an active, laterally propagating wedge thrust, Wheeler Ridge, California. In S. Mitra & G. W. Fisher (Eds.), Structural Geology of Fold and Thrust Belts (pp. 3–28). Baltimore: Johns HOpkins University Press.
  • Mueller and Talling, Journal of Structural Geology, 1997.
  • Keller, E. A., Zepeda, R. L., Rockwell, T. K., Ku, T. L., Dinklage, W. S., Barbara, S., & Street, G. (1998). Active tectonics at Wheeler Ridge , southern San Joaquin Valley , California. Geological Society of America Bulletin, 110(3), 298–310.
  • Kleber, E. J. (2015) Surface Response to Slip Along a Propagating Blind Thrust Fault Wheeler Ridge, California. M.S. thesis: Arizona State University, 95 pp.
• Demonstrative presentation (ppt) and (pdf)

Field trip in NW Himalaya (Himachal Pradesh)

I just returned from a very interesting and pleasant field trip in Himachal Pradesh (India) to examine the major elements of the frontal portion of the NW Himalaya. The trip was lead by Dr. Rasmus Thiede of the University of Potsdam (UP). This was my third trip to the Himalayas (the first in 2001 to the Sutlej and Spiti Rivers with UP colleagues including Rasmus and Bodo Bookhagen when they were starting their Ph.D.s under the supervision of Professor Manfred Strecker; the second was in 2010 with Dr. Wendy Bohon in the Ladakh region to contribute to her work along the Karakoram Fault in the Pangong Range area). We joined two UP students (Katharina Kretzschmar and Markus Nennewitz) who had been working in the area for two weeks already, focusing on developing a structural profile across the principal faults of the NW Himalaya in the region. I overlapped for a day with Dr. Saptarshi Dey who worked on his Ph.D. with Rasmus in the Kangra reentrant (see Dey, et al., 2016a,b). And, it was a pleasure to meet Professor Vikrant Jain from IIT Gandhinagar and his Ph.D. students. I did not (yet) get their last names but they were Ramindran, Sonam, and Pritha. Tashi Gyatseo is a long-time guide and friend of Rasmus who was chief of logistics for the trip. It was fun to meet everyone and to discuss the geology and geomorphology as well as learn a bit more of eachother's cultures.

Along with strengthening the collaborations among the groups, there were a couple of scientific targets of the trip. They build to a large degree from the Ph.D. work of Saptarshi Dey and focus on:

1. The role of climate modulation of the sediment supply and transport capacity along the major river systems and the development (and removal) of fluvial fills and terraces.
2. The activity of the major faults of the system, including the Himalayan Frontal Thrust and out of sequence faulting (activity higher in the tectonic wedge) possibly influenced by load variation from changes in sediment storage in the orogenic wedge.

So, we looked at a lot of interesting fluvial terraces mostly along the Ravi River system as well as reviewed the major structural elements of the system: HFT, Siwaliks, Main Boundary Thrust (MBT), and the Main Central Thrust (MCT).

Overview figure of the region from Gavillot, et al., 2016. The box shows the location of our trip and the map shown below.

Overview of the field trip with the orange-red line showing most of our tracks and the yellow points my main obversation locations. I am using the GaiaGPS app for my mapping. It seems ok but I might look for a more geologically oriented app for the next trip.

Panorama and annotated overlay showing the major structures and bounded rock units

Pictures

View of the nice mountains (Dhaula Dhar Range) from the Kangra airport--a nice way to start the trip!

Katharina, Markus, and Rasmus with the impressive Dhaula Dhar Range behind as seen from the Kangra area.

Most of the group at a stop along the Main Boundary Thrust where a spring may indicate increased permeability along the fault zone (yellow-white material at left is travertine).

Upper Siwaliks at sunset

Katharina in the MCT mylonites.

Chambo Town--built on an important probably 10 ka terrace. We spent a pleasant cool night there.

Pretty agricultural terraces on a high terrace south of Chamba.

Nice terraces near the Chemera Reservoir.

Stair step terraces in a tributary a few km below the Chemera Reservoir.

Rasmus is a great teacher and it was wonderful to learn from him. Here he is near some fine grained schists discussing their reflection of the overall deformation in the MCT zone.

References cited
Dey, S., Thiede, R., Schildgen, T., Wittmann, H., Bookhagen, B., Scherler, D., and Strecker, M. Holocene internal shortening within northwest Sub-Himalaya: Out-of-sequence faulting of the Jwalamukhi Thrust, India: Tectonics, 2016a.

Dey, S., Thiede, R. C., Schildgen, T. F., Wittmann, H., Bookhagen, B., Scherler, D., … Strecker, M. R. (2016b). Climate-driven sediment aggradation and incision since the late Pleistocene in the NW Himalaya, India. Earth and Planetary Science Letters, 449, 321–331. https://doi.org/10.1016/j.epsl.2016.05.050

Gavillot, Y., Meigs, A., Yule, D., Heermance, R., Rittenour, T., Madugo, C., & Malik, M. (2016). Shortening rate and Holocene surface rupture on the Riasi fault system in the Kashmir Himalaya: Active thrusting within the Northwest Himalayan orogenic wedge. Bulletin of the Geological Society of America, 128(7), 1070–1094. https://doi.org/10.1130/B31281.1

Short Course at LIPI : Techniques in Active Tectonic Study

In July 2013, Gayatri Marliyani and I taught a short course at LIPI in Bandung, Indonesia on Techniques in Active Tectonic study. I put together almost 30 lectures on various topics in active tectonics, neotectonics, tectonic geomorphology, paleoseismology, earthquake geology, and related topics. Special thanks to Mudrik Daryono (course coordinator for LIPI/ITB/GREAT), Irwan Meilano (ITB/GREAT), Danny Hilman Natawidjaja (LIPI/GREAT), Eko Yulianto (LIPI/GREAT), and the participants.

Gayatri built a nice website with all of the freely available lectures and other course content. We also recorded most of the lectures and they are on youtube.

The course web site is: http://activetectonics.la.asu.edu/lipi/. Look under the schedule link for the lectures and the link for some exercise content.

Group picture on field trip along the Lembang Fault.

Tours in Google Earth around Arizona highlight aspects of its geology

As a part of my final set of lectures for the 2012 Structural Geology class, I used my Camtasia to record some fly overs of Arizona from inside Google Earth.

In the first video (29 Mb MP4 format video file or on youtube), I tour from inside the Grand Canyon to around Flagstaff, Prescott and Jerome and finish over south Phoenix.

In the second video (29 Mb MP4 format video file or on youtube), I tour from the White Mountains of eastern Arizona over to Phoenix and on down to finish above Tucson.

These videos are not narrated, but they are then embedded in the narrated lecture on the Cordilleran geologic history (post Eocene) that I developed for the class (look around 20 minutes):
Tectonic history of the western North American Cordillera (from Eocene) ppt
video narration--big file (100MB)--may need to right click and save to local disk. Lecture narrated video on Youtube

videos

I hope these might be useful for others.