Rensselaer campus regulars may not be aware of it,
but earthquakes frequently surge through the base-
ment of the J. Erik Jonsson Engineering Center. Pro-
ducing a powerful shaking sensation, these seismic
events have taken a considerable toll, leaving behind
a trail of broken pipes, damaged pilings, and other
serious structural problems.
Not to worry, though. These earthquakes are actu-
ally scale-model simulations, generated by civil engi-
neers in Rensselaers recently redeveloped Geotech-
nical Centrifuge Center, part of the George E. Brown
Jr. Network for Earthquake Engineering Simula-
tion (NEES), a nationwide academic research con-
sortium. The tests often use Rensselaers centrifuge,
an imposing device with a mechanical arm that can
swing model structures around at 250 miles per hour,
exerting forces real buildings would face only at catas-
trophic moments.
We cannot wait 20 or 30 years for an earth-
quake to occur, says Ricardo Dobry, professor of
civil and environmental engineering and director of
the Geotechnical Centrifuge Center. This allows
us to test structures and full systems. Recent catas-
trophic natural disastersparticularly the Decem-
ber 2004 earthquake and tsunami originating in
Sumatra and the earthquake in Pakistan and India
in October, which have killed tens of thousands
underscore the importance of research in these areas.
Rensselaer researchers are working with colleagues around the
world to plumb the depths of the causes and effects of earthquak
es.
Earthquake researchers (clock-
wise from top left) Rob McCaffrey,
Steve Roecker, Tarek Abdoun, and
Ricardo Dobry in Rensselaers
150 g-ton geotechnical centrifuge
facility located in the basement of
the Jonsson Engineering Center.
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ENSSELAER
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BENEATH
WHAT LIES
M
ARK
M
C
C
ARTY
By Peter Dizikes
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hile Troy, like all of New York state, rarely expe-
riences significant seismic activity, Rensselaer
is a hive of research activity on the subject. Insti-
tute researchers stand at the leading edge of
studying both the causes and the effects of earthquakes,
examining everything from the physical construction
of fault zones to the safe construction of buildings in
those zones.
The Geotechnical Centrifuge Center is just one node
of earthquake research at Rensselaer. Institute earth
scientists have fanned out across the globe to perform
significant fieldwork for years, studying faults and earth-
quake activity from Kyrgyzstan to California and from
Indonesia to Oregon. Rensselaer research on earth-
quakes also engenders interdisciplinary projects: engi-
neers work with computer scientists, and geophysicists
collaborate with mathematicians. Earthquakes may be
an age-old problem, but the research methods used to
understand them are distinctly new.
I FEEL THE EARTH MOVE
Earthquakes are a product of the motion of the plan-
ets tectonic platesthe 20 or so large segments of the
Earths crust slowly moving around the globewhich
are responsible for the ongoing rearrangement of the
world we see. A head-on collision between tectonic
plates, which has happened at the edge of the Indian
subcontinent, can produce spectacular features such as
the Himalaya mountain range and the recent Kashmir
earthquake.
Tectonic plates do not always meet in this precise
fashion, however. When a plate largely supporting an
ocean meets a continent-bearing plate, the heavier
oceanic plate tends to dive underneath its neighbor, in
the process called subduction. And sometimes plates
scrape past one another in a lateral motion, as is the
case with the San Andreas Fault in California.
Whatever the precise movement, a single earthquake
represents the release of tension that accumulates along
a fault, where plates move in fits and starts. Its like a
spring getting loaded, says Rob McCaffrey, professor
of geophysics, who has helped pioneer the use of Glob-
al Positioning System (GPS) technology to measure the
movements of plates. The number-one question is how
much of the fault will go at one time, McCaffrey adds.
That determines the magnitude of the earthquake and
the duration of its shaking.
In geologic time, spanning billions of years, an indi-
vidual earthquake is a tiny, incremental event. In human
terms, however, as Dobry notes, major earthquakes are
infrequent (although small ones happen every day
around the globe). Yet that is only one reason engineers
need to generate their own steady stream of data through
simulated quakes.
With earthquakes, another big problem is, you never
know when or where theyre going to happen, says
Tarek Abdoun, assistant professor of civil engineering
and associate director of Rensselaers centrifuge cen-
ter. Whenever you put instruments in a certain area,
earthquakes never happen there. But for us, as engi-
neers, to be able to understand a certain phenomenon
and design for it, you need to know what is happening.
With a centrifuge, you have instrumentation, you can
recreate the event, you learn a lot, and now you can
improve the design and the foundation of buildings.
The sheer scale of the planet means researchers still
are just beginning to collect earthquake data in many
places. In the 1980s, McCaffrey was among the first sci-
entists to use GPS measurements in Indonesia, the site
of last years catastrophic earthquake. Today, much of
McCaffreys work involves measuring the buildup of
the energy right now in complex fault systems in order
to develop a detailed picture of fault activity and, even-
tually, a better sense of which fault segments might be
most prone to move in a given period.
Specific earthquake predictions remain an elusive
goal. The outlines of tectonic plates might look simple
on a world map, but the view from the ground is anoth-
er matter. Within a fault zone itself, tectonic plates do
not just neatly collide or grind past one another, but
can shatter into smaller pieces, like a fractured eggshell.
The more scientists measure subduction zones, the more
they realize how complicated they can beespecially in
places like Sumatra.
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Professor Steve Roecker is part
of a team of researchers study-
ing the Tien Shan mountains in
Central Asia, considered a geo-
logic puzzle because they exist
not at the edge of a tectonic
plate, but in the middle of one.
The house, above, sits at the
base of tilted strata.
Rensselaer earth scientists have fanned
out across the globe to perform significant
fieldwork for years, studying faults and
earthquake activity from Kyrgyzstan to
California and from Indonesia to Oregon.
S
TEVE
R
OECKER Its not just a simple subduction, says McCaffrey,
who over the years has become something of a special-
ist in such regions, including Oceania and the Pacific
Northwest of the United States. What New Zealand
and Cascadia and Sumatra have in common is that the
upper plate in the system is breaking apart and forming
these little plates that are moving around indepen-
dently. Oregon, for example, sits on a small plate rotat-
ing clockwise relative to the rest of the United States.
Such intricacies make charting the mechanics of a fault
zone much more difficult.
JOURNEY TO THE CENTER OF THE EARTH
The challenges inherent to earthquake research do not
daunt Rensselaer researchers. The fact that the Earth
is complicated, well, thats what you have to deal with,
says Steve Roecker, professor of earth and environ-
mental sciences. Roecker is undertaking multiple pro-
jects designed to help reveal, case by case, what sub-
stances lie underneath faults, and how these materials
relate to their motion.
Roecker spent the summer of 2005 in Kyrgyzstan,
studying the Tien Shan mountainsconsidered a geo-
logic puzzle because they exist not at the edge of a tec-
tonic plate but in the middle of one, the Eurasia Plate.
The real mystery is why there are mountains there at
all, Roecker says. Its possible that there could be a
large fault covered up by the mountains, or a series of
smaller fractures near the Earths surface that act like
miniature plate boundaries.
To study the Earths insides, Roecker sets up net-
works of seismometerssensitive measuring devices
and records the speed of the waves generated by earth-
quakes. For a geophysicist, this data reveals much about
the materials lying underground. High-temperature
rocks, for instance, slow down earthquake waves. Recent
technological advances now allow small seismometers
to pick up waves originating far away. Were able to
make some nice pictures just by setting up instruments
and waiting for an earthquake to happen anywhere in
the world, says Roecker.
For the Tien Shan project, those pictures may involve
the Earths mantle, the viscous layer underneath the
crust that ranges roughly 20 to 2,000 miles below the
Earths surfacea distance almost impossible to reach
with todays technology. By contrast, in California,
Roecker is part of a project called the San Andreas
Fault Observatory at Depth, an attempt to drill just a
couple of miles into the Earths surface. Scheduled for
completion in 2006, it aims to reveal what substances
enable plates to slip and slide past one another (under-
ground water is a prime suspect).
Roeckers efforts to turn the data into maps of the
Earths interior, at any depth, are often conducted with
colleagues at Rensselaers Inverse Problems Center,
including mathematicians Margaret Cheney and Joyce
McLaughlin, who have years of relevant experience
from analogous areas like medical imaging. They have