Geophysical Research Letters
Supporting Information for
Shallow mantle velocities beneath the southern Appalachians from Pn phases
Julia G. MacDougall1*, Karen M. Fischer1, Donald W. Forsyth1, Robert B. Hawman2, Lara S.
Wagner3
1Department
of Earth, Environmental, and Planetary Sciences, Brown University, Providence, Rhode Island, USA,
of Geology, University of Georgia-Athens, Athens, Georgia, USA, 3Department of Terrestrial
Magnetism, Carnegie Institution for Sciences, Washington, DC, USA, *now at Department of Earth and Atmospheric
Sciences, University of Houston, Houston, Texas, USA
2Department
Contents of this file
Figures S1 to S3
Introduction
These three figures supply additional information described in the text, including record
sections of the Virginia and Kentucky earthquakes that were used in the cross-correlation
analysis (bandpass: 0.5-2.0 Hz) to calculate the arrival-time differences for station pairs in our
study area, a full record section of the Virginia earthquake (bandpass: 0.5-2.0 Hz), and a
diagram of the parameters we use in our iterative solution scheme.
1
Figure S1. Vertical component seismograms for the a) 23 August 2011 Mineral, Virginia and b)
10 November 2012 Whitesburg, Kentucky earthquakes. Waveforms were normalized to a CMG3T instrument response and causally filtered at 0.5-2 Hz. Time was reduced by a velocity of 8
km/s, and waveform amplitudes were multiplied by epicentral distance (in km). Pink bars show
representative waveform windows used to obtain differential times by cross-correlation. Blue
arrows show examples of Pn onsets in time; Pn is observed at the D-line stations for the Virginia
earthquake but onsets are not marked. Only waveforms contributing differential times to this
study are shown. Pn phases arrive first without interference from later phases. The one
exception is the Kentucky earthquake waveform at station W53A in which direct P arrives at a
time close to Pn, leading us to calculate mantle velocities for North group differential times
with and without W53A.
2
Figure S2. Vertical component seismograms for the 23 August 2011 Mineral, Virginia
earthquake, including SESAME and permanent station waveforms not used in the solving for
mantle velocities because the station did not form a pair with another within the 3.1° limit for
differences in back-azimuth. Waveforms were normalized to a CMG-3T instrument response
and causally filtered at 0.5-2 Hz. Time was reduced by a velocity of 8 km/s, and waveform
amplitudes were multiplied by epicentral distance (in km). This record section demonstrates
that Pn phases arrive first with minimal interference from later phases at least to the maximum
distance of 7° used in this study.
3
Figure S3. Parameters used in solving for mantle P-wave velocity. HA and HB, VA and VB, and θA
and θB are the crustal thicknesses, crustal velocities, and critical angles beneath the near and far
stations in a differential time pair, respectively. In this example, the near station is on the
SESAME D-line and the far station is on the W-line. Dashed purple lines represent the crustal
path lengths beneath each station, and the blue line is the mantle path length difference
(corresponding to the horizontal axis in Figure 3). Vm is mantle velocity. α represents the dip of
the Moho.
4