16.6 MB pdf - IRIS

ealistic shaking scenarios for regional demonstration projects
with physics-based simulations of damage and improved
earthquake hazard and loss assessment. The development of
such new insights is accelerated dramatically by earthquakes
or eruptions of particular significance, but the timing of these
events cannot be anticipated. Thus, we must be ready by operating
a fiducial network of seismic observatories, maintaining
state-of-the-art portable instruments that can be deployed
rapidly when important earthquake and volcanic eruption
sequences occur, and developing capabilities for rapid
warning of earthquake shaking.
Change and Interactions Among Climate,
Hydrology, Surface Processes, and Tectonics
How do Earth dynamics and structure relate to the distribution
of freshwater and energy resources? How do the coupled systems
respond to natural and anthropogenic forcing?
Seismology has an overwhelmingly important role to play in
the development of energy options for the 21 st century, and
is an important complement to other geophysical techniques
in managing water resources. PASSCAL and FA deployments
increasingly facilitate 3D seismic imaging at the reservoir
and basin scales that are of central importance to oil and gas
exploration and to optimal management of existing fields.
Induced earthquakes monitored by networked instruments
have had impacts on geothermal energy, where they have led
to operations being shut down. Induced earthquakes have
also had an impact on shale gas development where they have
been implicated in operations to re-inject flowback water. If
CO 2 sequestration is to happen at a scale to mitigate climate
change, induced earthquakes are likely to place important
constraints on that activity as well. The future of nuclear
power plant construction and high-level radioactive waste
disposal is critically dependent on developing a predictive
understanding of earthquake behavior, particularly in areas
of low seismic hazard.
A new generation of integrated power and data acquisition
systems developed by experienced PASSCAL and
UNAVCO engineers has facilitated growth and success of the
Polar Earth Observing Network (POLENET)—a project to
collect seismic and geodetic data from autonomous systems
deployed at remote sites spanning much of the Antarctic ice
sheet to answer critical questions about their behavior in a
warming world. Combining these POLENET measurements
with ground-based measurements of gravity, sea level, and the
atmosphere and with satellite measurements will lead to better
ice sheet budgets, link ice sheet change to the global Earth
system, and provide a deeper understanding of how polar ice
sheets contribute to changing sea levels around the world.
IRIS’s role in the Greenland Ice Sheet Monitoring Network
(GLISN) has established a real-time array of seismic stations
Glacial and Iceberg “Earthquakes”
Recent deployments of broadband seismometers on ice sheets
and icebergs have recorded breakup in the Ross Sea near
Antarctica, calving of ice off the end of glaciers, and iceberg
fracturing. The records are yielding new insights into these
processes, which may be accelerating due to climate change.
Glacial earthquakes were discovered recently as low-frequency
signals in seismograms from the GSN. Many of the events that
occur during the late summer along the coasts of Greenland
are clustered near large outlet glaciers. The rate of glacialearthquake
occurrence varies from year to year, increasing
quickly between 2000 and 2005 but continuing at a steady
rate more recently. Variations in glacier-terminus position and
retreat rate between seasons and between years account in
general for variation in the rate of occurrence of glacial earthquakes.
Seismological measurement of glacier and iceberg
dynamics adds a new tool both for monitoring and for retrospective
studies of 20 th century activity, but on-site investigations
to discover the mechanisms by which glacial phenomena
generate seismic signals are needed to maximize returns from
multidisciplinary data analysis.
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GPS/NRS
GPS/Gonz
Camera
Helheim Network 2009
Seismometer
AWS
Tide gauge
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“Studies of Earthquakes and Rapid Motions of Ice” used PASSCAL and
other instruments to focus on East Greenland’s two largest outlet glaciers,
Helheim glacier and Kangerdlugssuaq glacier. This map shows
seismological, geodetic, photographic, and other systems used for local
monitoring of Helheim glacier during the summer of 2009, collected
in the field and via remote sensing, to build an understanding of flow
dynamics and short-timescale glacier behavior. The data demonstrated
that the times of glacial earthquakes are strongly correlated with large
calving events, which result in rapid changes in glacier speed. The seismic
signals were generated by impacts on the face of the glacier and the
underlying solid Earth when cubic-kilometer-scale icebergs capsized.
(Nettles and Ekström, 2010)
I-12 VOLUME 1 | Section I | Scientific Justification