Auxiliary Material for
Observations of Static Coulomb Stress Triggering of the November 2011 M5.7
Oklahoma Earthquake Sequence
Danielle F. Sumy1, Elizabeth S. Cochran2, Katie M. Keranen3,
Maya Wei4, and Geoffrey A. Abers5
1
National Science Foundation Earth Sciences Postdoctoral Research Fellow at the United
States Geological Survey, Pasadena, California, USA
2
United States Geological Survey, Pasadena, California, USA
3
ConocoPhillips School of Geology and Geophysics, University of Oklahoma, Norman,
Oklahoma, USA
4
Department of Geological Sciences, Brown University, Providence, Rhode Island, USA
5
Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York, USA
Journal of Geophysical Research, Solid Earth, 2014
Introduction
We examine the Coulomb (ΔCFF) and/or shear stress (Δτ) change as a function of the
effective coefficient of friction (μ’) in these auxiliary tables. In ts01.docx, we examine
the ΔCFF as a function of μ’ between 0.0-0.8 for the 110 HASH-derived focal
mechanism solutions, described in the text and listed in Table C1. We perform 2000
random resamples of the HASH-derived focal mechanism solutions following each of the
three M≥5 earthquakes (Events A-C, respectively), and report the average ΔCFF when
the μ’= 0.4 and when μ’=0.0 (or simply the Δτ) in ts02.docx. Furthermore, we examine
the ΔCFF on the specified fault plane solution and the Global Centroid Moment Tensor
solution, respectively, as a function of μ’, for aftershocks of Events A-C is ts03.docx.
Finally, in ts04.docx, we examine the ΔCFF for all unique focal mechanism-hypocenter
combinations for events that follow each Event A-C, respectively.
1. ts01.docx Coulomb Stress Change (ΔCFF in bars) as a function of μ’.
1.1 Column “μ’”, dimensionless, effective coefficient of friction.
1.2 Column “N”, number of earthquakes examined.
1.3 Column “ΔCFF<-0.1”, bars, number of earthquakes that exhibit Coulomb stress
change less than -0.1 bars.
1.4 Column “-0.1≤ ΔCFF≤ 0.1”, bars, number of earthquakes that exhibit Coulomb stress
change between -0.1 to 0.1 bars.
1.5 Column “ΔCFF>0.1”, bars, number of earthquakes that exhibit Coulomb stress
change greater than 0.1 bars.
2. ts02.docx Average stress change results after 2000 bootstrap resamples.
2.1 Column “Aftershocks of”, the aftershocks of each M≥5 earthquake, Events A-C
respectively.
2.2 Column “N”, number of aftershocks with HASH-derived focal mechanism solutions
that follow each M≥5 event.
2.3 Column “<-0.1 bars”, earthquakes that exhibit ΔCFF and/or Δτ less than -0.1 bars.
2.4 Column “-0.1 - 0.1 bars”, earthquakes that exhibit ΔCFF and/or Δτ between -0.1 to
0.1 bars.
2.5 Column “>0.1 bars”, earthquakes that exhibit ΔCFF and/or Δτ greater than 0.1 bars.
3. ts03.docx Coulomb stress change (ΔCFF) for aftershocks as a function of μ’
3.1 “μ’”, dimensionless, effective coefficient of friction.
3.2 “N”, number of earthquakes following each of the M≥5 earthquakes, Events A-C
respectively.
3.3 Column “ΔCFF<-0.1”, bars, number of earthquakes that exhibit Coulomb stress
change less than -0.1 bars.
3.4 Column “-0.1≤ ΔCFF≤ 0.1”, bars, number of earthquakes that exhibit Coulomb stress
change between -0.1 to 0.1 bars.
3.5 Column “ΔCFF>0.1”, bars, number of earthquakes that exhibit Coulomb stress
change greater than 0.1 bars.
4. ts04.docx Coulomb stress change (ΔCFF in bars) for aftershocks (μ’ = 0.4).
4.1 “Earthquakes”, examination of events following each Event A-C, respectively.
4.2 “N”, number of possible unique focal mechanism-hypocenter combinations following
each of the M≥5 earthquakes, Events A-C respectively.
4.3 Column “ΔCFF<-0.1”, bars, number of earthquakes that exhibit Coulomb stress
change less than -0.1 bars.
4.4 Column “-0.1≤ ΔCFF≤ 0.1”, bars, number of earthquakes that exhibit Coulomb stress
change between -0.1 to 0.1 bars.
4.5 Column “ΔCFF>0.1”, bars, number of earthquakes that exhibit Coulomb stress
change greater than 0.1 bars.
5. fs01.eps (Figure S1) Map of aftershocks from the catalog of Keranen et al. [2013] that
follow the (a) M5.0 foreshock (Event A), (b) the M5.7 mainshock (Event B), and (c) all
three M≥5 events (Events A-C). We record the number of aftershocks (N) in each
subplot, and show the three M≥5.0 events (black stars), which are placed at their
Oklahoma Geological Survey (OGS) locations with focal mechanisms from the Global
Centroid Moment Tensor (GCMT) catalog. Thick black lines represent the surface
projection of the rupture planes of each M≥5.0 earthquake.