propagate away from the wells and disturbs a
larger and larger volume, the probability increases
that fluid pressure will encounter a larger fault and
induce a larger-magnitude earthquake. The absence of earthquakes in regions above the critical
pressure threshold may result from either a lack
of faults or lack of well-oriented, critically stressed
faults. Alternatively, fluid flow may preferentially
migrate along bedding structure (Fig. 2A).
Though seven earthquakes were recorded in
2006 to 2009 near the base of the SE OKC
wellbores (10), the main swarm began ~15 km to
the northeast (fig. S9), despite the high modeled
pressure perturbation near the wells. Earthquakes
in 2009 primarily occurred, within location uncertainty, near injection wells or on the nearest
known faults to the northeast of the wells (fig. S9).
Focal mechanisms near the swarm onset indicate
fault planes at orientations favorable to failure
(19) (Fig. 2, inset B). Faults subparallel to the
north-northwest–south-southeast–trending
Nemaha fault would not be well oriented for
failure in the regional ~N70E stress regime (25)
and would require substantially larger pressure
increase to fail. Recent earthquakes near the fault
may be evidence for continued pressure increase.
This 50-km-long segment of the Nemaha fault is
capable of hosting a M7 earthquake based on
earthquake scaling laws (20), and the fault zone
continues for hundreds of kilometers. The increasing proximity of the earthquake swarm to the
Nemaha fault presents a potential hazard for the
Oklahoma City metropolitan area.
Our earthquake relocations and pore pressure
models indicate that four high-rate disposal wells
are capable of increasing pore pressure above the
reported triggering threshold (21–23) throughout
the Jones swarm and thus are capable of triggering ~20% of 2008 to 2013 central and eastern
U.S. seismicity. Nearly 45% of this region’s seismicity, and currently nearly 15 M > 3 earthquakes
per week, may be linked to disposal of fluids generated during Oklahoma dewatering and after
hydraulic fracturing, as recent Oklahoma seismicity dominantly occurs within seismic swarms in
the Arbuckle Group, Hunton Group, and Mississippi Lime dewatering plays. The injection-linked
seismicity near Jones occurs up to 35 km away
from the disposal wells, much further than previously considered in existing criteria for induced
seismicity (13). Modern, very high-rate injection
wells can therefore affect regional seismicity and
increase seismic hazard. Regular measurements
of reservoir pressure at a range of distances and
azimuths from high-rate disposal wells could verify our model and potentially provide early indication of seismic vulnerability.
REFERENCES AND NOTES
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portion of the contiguous United States east of 109°W.
10.AN SS catalog, United States Geological Survey, http://
earthquake.usgs.gov/earthquakes/search/, accessed 4/1/2014.
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29. Monthly average volume was calculated by using reported
volumes for any month with nonzero volume in data available
from 1995 through 2012 (15). Injection rates over 90% larger
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were removed from calculations to remove data entry errors.
ACKNOWLEDGMENTS
This research benefited from discussion with E. Cochran, W. Ellsworth,
and participants in a U.S. Geological Survey (USGS) Powell Center
Working Group on Understanding Fluid Injection Induced Seismicity
(M. W., B. A.B., and S.G. are part of this group). C. Hogan identified many
P and S phases. K.M. K was partially supported by USGS National
Earthquake Hazards Reduction Program (NEHRP) grant G13AP00025,
M. W. was partially supported by the USGS Powell Center grant
G13AC00023, and G.A.A. was partially supported by NEHRP grant
G13AP00024. This project used seismic data from EarthScope’s
Transportable Array, a facility funded by the National Science
Foundation. Seismic waveforms are from the Incorporated Research
Institutions for Seismology Data Management Center and the USGS
CWB Query. Well data are from the Oklahoma Corporation Commission
and the Oklahoma Geological Survey. Lists of wells and the local
earthquake catalog are available as supplementary materials on
Science Online.
SUPPLEMENTARY MATERIALS
www.sciencemag.org/content/345/6195/448/suppl/DC1
Materials and Methods
Figs. S1 to S10
Tables S1 to S9
References (30–41)
8 May 2014; accepted 24 June 2014
Published online 3 July 2014;
10.1126/science.1255802
DINOSAUR EVOLUTION
A Jurassic ornithischian dinosaur from
Siberia with both feathers and scales
Pascal Godefroit,1 Sofia M. Sinitsa,2 Danielle Dhouailly,3 Yuri L. Bolotsky,4
Alexander V. Sizov,5 Maria E. McNamara,6,7 Michael J. Benton,7 Paul Spagna1
Middle Jurassic to Early Cretaceous deposits from northeastern China have yielded varied
theropod dinosaurs bearing feathers. Filamentous integumentary structures have also been
described in ornithischian dinosaurs, but whether these filaments can be regarded as part of
the evolutionary lineage toward feathers remains controversial. Here we describe a new basal
neornithischian dinosaur from the Jurassic of Siberia with small scales around the distal
hindlimb, larger imbricated scales around the tail, monofilaments around the head and the
thorax, and more complex featherlike structures around the humerus, the femur, and the
tibia. The discovery of these branched integumentary structures outside theropods suggests
that featherlike structures coexisted with scales and were potentially widespread among the
entire dinosaur clade; feathers may thus have been present in the earliest dinosaurs.
The origin of birds is one of the most-studied iversification events in the history of life. Principal debates relate to the origin of key avian features such as wings, feathers, and flight (1–9). Numerous finds from China
have revealed that diverse theropods possessed
feathers and various degrees of flight capability (4–9). The identification of melanosomes in
non-avian theropods (10, 11) confirms that fully
birdlike feathers originated within Theropoda
at least 50 million years before Archaeopteryx.
But were feathers more widespread among
dinosaurs? Quill-like structures have been re-
ported in the ornithischians Psittacosaurus (12)
and Tianyulong (13), but whether these were true
feathers, or some other epidermal appendage, is
unclear. Bristlelike epidermal appendages occur
in pterosaurs, some early theropods (14), and ex-
tant mammals (“hairs”), and so the Psittacosaurus
SCIENCE
sciencemag.org 25 JULY 2014 • VOL 345 ISSUE 6195 451
1Directorate ‘Earth and History of Life,’ Royal Belgian
Institute of Natural Sciences, Rue Vautier 29, B-1000
Brussels, Belgium. 2Institute of Natural Resources, Ecology
and Cryology, 26 Butin Street, 672 014 Chita, Russia.
3UJF-CNRS FRE 3405, AGIM, Université Joseph Fourier,
Site Santé, 38 706 La Tronche, France. 4Institute of Geology
and Nature Management, FEB RAS, 1 Relochny Street 675
000, Blagoveschensk, Russia. 5Institute of the Earth Crust,
SB RAS, 128 Lermontov Street, Irkutsk, 664 033 Irkutsk,
Russia. 6School of Biological, Earth and Environmental
Science, University College Cork, Cork, Ireland. 7School of
Earth Sciences, University of Bristol, Bristol BS8 1RJ, UK.
*Corresponding author. E-mail: pascal.godefroit@
naturalsciences.be
RESEARCH | REPORTS
