Dr. Kristy Tiampo, Director Dr. Pablo Gonzalez My research interests are focused, mainly, on the
understanding of the mechanisms that promotes Earth's surface
deformation and stress conditions in and around volcanoes and fault
zones. I use a combination of techniques from structural geology,
geodesy and computer modelling to adress the questions about the
mechanics of magmatic systems and earthquake faulting, and its
spatio-temporal evolution. My current research interests includes
volcano flank deformation, time-dependent deformation in shallow
magmatic systems, continental deformation at diffuse plate boundaries,
and mechanics of extensional deformation at plate-boundary scale. Volcano geomechanics: Using a combination of structural
geology, geophysical propecting methods and geodetic data, I have
studied how the volcanoes deforms. For example, how a repeated sets of
microgravity surveys soon after a period of unrest could serve for the
monitoring of fluid migrations after a dike intrusion (Gottsmann et al.,
2006). Also a hot topic in volcano geodesy is the evaluation of
structural stability of volcanic edifices and the study of frictional
and kinematic properties of basal (decollements) and intra-volcanic
fault systems (González et al., 2010b). In general, the development of
ground deformation monitoring systems (Perlock et al., 2008; Prieto et
al., 2009).
Continental deformation at diffuse boundary lithospheric
plates: I am interested in the understanding of the nature of
continental deformation primarily using geodetic data from GPS networks
or satellite radar interferometric surveys to bring us with
instantaneous (present-day) deformation kinematics to long-standing
views from geomorphology and structural geology. I have started to
analyse some recent earthquakes using radar interferometry (González et
al., 2009) to more developed models of co- and postseismic deformation
of high-strain deformation areas to understand the role of such areas
in a low rate convergence diffuse plate boundaries (Gonzalez et al., in
preparation). In the future, I am interest to develop kinematics
models to explain current deformation partition at such low rate
convergence diffuse plate boundaries. Dr. Amir Tavakoli I have been working under the supervision of
professor Kristy Tiampo as a post-doctoral fellow since July 2009. Our
main goal is to contribute in modeling and simulation of earthquakes. To
this end we choose to work on Virtual California (VC). In parallel, we
are studying the gravity gradient and its effect on earthquakes. VC is an existing simulation code which has
been developed and updated during the current decade. The input to VC is
the geometry of fault system along with the friction and other forces.
In VC the main objective is to produce an artificial earthquake and see
the effect of it in a fault system. This process can be done back and
forth to produce a complete catalogue. Comparing the catalogue with the
real data from the past history of specific fault system can help to
improve our picture. It also might be an excellent assistance to
forecast the future of events in a region. Samira Alipour, Ph.D. candidate My primary interest is applications of
InSAR (Interferometric Synthetic Aperture Radar) and PolInSAR
(Polarimetric Interferometric Synthetic Aperture Radar) techniques to
image ground-surface deformation related to the natural or man-made
processes, such as volcanic or tectonic activities or mining induced
subsidence. Attieh Eshaghi, Ph.D. candidate
Earthquake early warning systems hold the potential to reduce
the damaging effects of earthquakes by giving a few seconds to a few
tens of seconds warning before the arrival of damaging ground motion.
Using P-wave arrivals is the most rapid method of delivering
earthquake early warning and may permit a few seconds warning of
ongoing ground motion in the region. The possible warning time is
usually in the range of up to 70 seconds, depending on the distances
between seismic sources, seismic sensor and user sites. Two approaches
are possible (Kanamori (2005)): a) Regional (front detection) warning,
b) on-site (or site-specific) warning. In (a), the traditional
seismological method is used to locate an earthquake, determine the
magnitude, and estimate the ground motion at other sites. In (b), the
beginning of the ground motion (mainly P wave) observed at a site is
used to predict the ensuing ground motion at the same site. I want to explore a practical approach to
earthquake early warning in Cascadia Subduction Zone in Canada's west
cost by determining earthquake early warning parameters. These parameters include a ground-motion period parameter τc and a high-pass filtered displacement amplitude parameter Pd from the initial 3 s of the P waveforms recorded at the Natural Resources Canada's Seismic Network stations for earthquakes with M >4.0. At a given site, I want to estimate the magnitude of an event from τc and the peak ground-motion velocity (PGV) from Pd. I want to investigate if there is a relationship between τc and magnitude (M), and between Pd and PGV for this area. These two relationships can be used to
detect the occurrence of a major earthquake and provide on-site warning
in the area around the station where onset of strong ground motion is
expected within seconds after the arrival of the P wave. Also I want to investigate the possible use
of 1 HZ GPS data for seismology fields. The Global Positioning System
(GPS) is a powerful tool for Earth studies, capable of representing
displacements occurring over a range of temporal and spatial scales.
These GPS data are important both for resolving the geodetic signature
of the earthquake itself and studies of
postseismic deformation. There are new efforts to use these data in
risk reduction assessment and even in earthquake and early warning
systems. Previous studies demonstrated that high-rate GPS accurately
measures large-amplitude motions. Javad Kazemian, Ph.D. candidate It is possible to compare earthquakes with
the brittle failure of homogeneous materials. Originally, a fracture
starts with the arbitrary appearance of damage in the form of
microcracks, after that probably a coalescence of microcracks which can
be a start of overall failure happens and finally the final crack
develops in the region with higher damage. The method of propagation of the crack is
still not well defined due to the complication of the precise shape of
the crack and the stress field acting on it. While failure of the
material is a complex phenomenon it can be simulate in some models. In this perspective, the focus is on the
case in which the fracture dynamics is continuous and slow, so that in
spite of possibly very fast local developments, a sample can be
considered in a quasi-equilibrium. This means that the sample internal
state is either independent of time or evolves slowly with respect to
the fast time-scale of the fracture process. The outcome, in general,
depends on the loading conditions, the crack geometry, and other
details in the engineering mechanics literature. To avoid all these
complications, one can disregard the dynamics of individual microcracks
and treat the damage at a coarse-grained scale. This approach, known
as ‘‘damage mechanics’’, is valid when the interaction among cracks is
moderate. In the simplest case, one can consider the evolution of a
scalar-valued damage field, describing the local variations of the
Hooke’s law σ(x) = E0(1-D(x))ε.The
idea behind damage mechanics is that all the complications of the
fracture process can be encoded in the field “D”. Simple models of
statistical fracture can be used to check some of the typical
assumptions and possible outcomes in damage mechanics. I chose to work on the Random Fuse Model
(RFM) which has been the cornerstone in this respect for the last 20
years. There is a formal analogy between the scalar elasticity problem
and an equivalent electrical problem; one identifies the current I with
the stress, the voltage V with the strain, and the conductivity, with
the Hooke tensor. The Random Fuse Model uses this electrical analogy.
This Model (RFM) is a simple idealized model to describe breaking
processes by increasing the current-carrying properties of a random
network consisting of insulators and fuses. By increasing the value of
the external voltage applied across the network, a sequence of fuses
will “burn out” and change irreversible into insulating bonds. This
process terminates when a contacting path no longer exists in the
network. This scalar electrical analogy of elasticity is a
simplification over the Lame´ equations (), and formally corresponds to
an antiplanar shear deformation scenario. Troy Unrau, M.Sc. candidate I am a M.Sc. candidate in Geophysics under the multidisciplinary
Planetary Sciences Program. My research focus is radar with
applications in the planetary sciences. To this effect, I principally
do research using ground penetrating radar (GPR) in the field and via
computer simulation to help determine the usefulness of this technique
for future surface exploration missions. Primary field work has been
in locations on Earth where the environmental conditions permit
research to be done as an analogue to Mars or the Moon. The primary
target is the scattering media and their effect on radar penetration. In additional to ground based GPR for planetary work, the results will
be applicable to any radar propagation problem in scattering media,
such as glacial tills. By borrowing methods from Polarimetric SAR
which are designed to characterize scattering mediums and textures,
information about the nature of the medium may be derivable from the
data. Lastly, I am involved in secondary projects: 1) processing large SAR
datasets in support of seismic deformation monitoring; 2) mission
control scientist for the Mistastin Crater Analogue Mission. Claire Mortera, Research Assistant Claire started working with Kristy and her
team in September of 2009.. The following are the major foci of her
work as Research Assistant: Collects high precision GPS data from
several stations across Ontario and Quebec. The data is then converted
into a standard format, processed, and archived for future research.
Selects and downloads remote sensing data based on specified parameters
such as satellite wave-length, acquisition date, polarization mode and
file format using various database program including DESCW, EOLI and
Google Earth for research projects. Gathers website data and assists in
website layout, design and maintenance, researches and downloads
scientific papers for references. Her organizational, financial and
administrative duties include but not limited to organizing and managing
software licensing and renewal, inventory of computer software and
hardware, storage of archived remote sensing data to ensure security and
backup, assists with logistics for Geology field course including
reservations for hotels, airline tickets, busing and other means of
transportation, manages customs regulations and forms on all
international shipments,assists students in expense claims preparation,
safety certification and purchasing procedures. Jon Lee Jonathan is working as a computer programmer
for Kristy Tiampo during the summer of 2010, continuing projects
started the previous summer. These projects include porting,
maintaining, and writing earthquake models for Kristy, as well as
writing software simulating microbial behavior for a joint project
between Kristy and Neil Banerjee. The earthquake models were cellular automata
and originally implemented in Perl. Jonathan updated these with an
interface that allowed pausing and stepping through individual steps in
the model, as well as options for visualizing the model in 3D.
Additionally, in the process the code was ported to C++ which in turn
reduced computational demands. The removal of some of this overhead
allowed for complexities to be added to the model, such as further
interactions between cells. Eventually other restrictions were lifted.
One of the next to go was the artificial structure of the cells, which
are placed on a perfect, square lattice. From observations of the
cellular model, it was conjectured that this structure favoured
propagation of events parallel to the automata's axes. To address this
concern, the cell structure was replaced by a planar graph of connected
nodes. The nodes were distributed randomly (but evenly) in the plane,
breaking the highly synthetic structure. The resulting model appeared
to propagate events in a far more natural manner. Besides Kristy's interest in earthquakes,
Jonathan has also worked on a model of microbial growth. This model
originally began as a work study project for Neil Banerjee. Neil is
studying tubule formations found in ancient glass, and has hypothesized
that these are caused by early living organisms. After extensive
physical research, he had the idea of simulating these tubules with a
computer and hired Jonathan to make the idea a reality. The simulation
was well received, and has since been used to create data to compare
with measured statistics. Using the simulation, it is possible to
explore how control of quantified factors affects qualitative
observations. Finally, and related to the microbe model,
Jonathan has begun writing an image recognition program used for
generating statistics from thin slices of the tubules. This program
takes a photographic image as input and trace the path of the tubules
within it. These paths are then interpreted as measurements of the real
data. Essentially, the program automates the time consuming and
inaccurate process of tracing each path by hand, and measuring with a
ruler. An additional feature is planned for the program: the partial
reconstruction of tubes in 3D by stitching together parallel thin
slices.Computational Laboratory for Fault System Modeling, Analysis, and Data Assimilation
Personnel
List of publications
Development of new methods and analysis tools of geodetic data:
During my PhD, I was, mainly, involved in three geodetic data analysis
problems i) how to obtain accurate measurements of horizontal
ground deformation at a comparable scale of InSAR techniques (González
et al., 2010a), ii) the development of new methods for the
retrieval of spatially continous 3D surface deformation for the
improvement of our capability of modelling processes using
geomechanical models of faulting and magmatic emplacement in the crust
(González et al., 2009; González, 2010), as well as iii) the
development of error analysis tools for evaluate the confidence in the
SBAS interferometric methods (González et al., in preparation). I am
always interested on new and wide branch applications of geodetic data
(Seco et al., 2009).
Mechanics of extensional deformation at plate-boundary scale:
Here, we are working in our project in the East African Rift funded by
the European Center for the Geodynamics and Seismology (ECGS) at
Luxembourg, to detect steady-state and transient deformation at long
spatialscales in extensional tectonics. 
Part of my thesis will be the integration of
polarimetric and interferometric observations. PolInSAR is an
advanced technique that makes it possible to separate different
scattering centers inside a resolution cell. By varying the
polarization states, optimal scattering mechanisms will be obtained.
Using this technique, it is possible to reduce the uncertainty in
interferometric phase estimation. Integration of polarimmetry with
the advanced Interferometric techniques aims at ground deformation
mapping with millimeter precision.
My thesis will also focus
on the inversion of InSAR observations which is a direct
manifestation of the processes that lead to surface deformation. I
invert InSAR data to retrieve the source parameters of the ongoing
process using an elastic dislocation models. Using the physical
models we are able to have a better understanding of the underlying
processes.
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Contacts
earth-sc@uwo.ca
519-661-3187
B&GS 1026
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