[unav_all] Webinar: Infrasonics and the USArray
andyf at iris.edu
Fri Sep 14 15:15:51 MDT 2012
The IRIS Transportable Array Working Group invites you to attend a
webinar on "Infrasonics and the USArray" on September 26, 2012 from 2-3
pm EDT (6-7 pm UTC).
Space for 100 attendees during the webinar is available on a first come,
first serve basis. If you are interested, please reserve a spot now:
After registering you will receive a confirmation email containing
information about joining the webinar. Following the presentation there
will be the opportunity for questions with the speaker. More information
on IRIS research webinars, including links to previously recorded
presentations, may be found here: http://www.iris.edu/hq/webinar/.
Please contact Andy Frassetto (andyf at iris.edu) with any additional
questions, concerns, or suggestions.
Presenter: Dr. Kristoffer T. Walker, University of California, San Diego
Summary: Atmospheric infrasound travels thousands of kilometers with
little attenuation in atmospheric waveguides controlled by the
temperature and wind structure. While Infrasonics shared a spot with
Seismology during the proliferation of nuclear weapons in the early to
mid 20th century, the ratification of the 1963 Limited Test Ban treaty
pushed nuclear testing underground and interest for infrasound
subsequently diminished. Recently, the adoption of the 1996
Comprehensive Test Ban Treaty has led to a renewed interest in
Infrasonics and the development of a 45-station global infrasonic array
network. Hundreds of infrasonic studies have been published since then,
and the average number of infrasound-related presentations at the Fall
AGU Meeting is at an all-time high of about 40. These studies show that
infrasound is a tool for a number of academic and practical studies.
Infrasound can be used to study hypotheses surrounding natural events
such as earthquakes, meteors, volcanoes, ocean wave interaction, aurora
processes, meteorological vortices, and mass-wasting processes.
Infrasound can also be used to measure the degree of anthropogenic
activity in cities, as well as locate explosions, rocket launches, and
jet trajectories. Atmospheric processes such as turbulence and the
interaction of gravity waves can also be constrained with infrasound.
Our ability to predict temperature and wind as a function of altitude
have progressed to the point that one can now use these models as
starting models to invert for second-order structure, which is useful
above the middle stratosphere where direct measurements of winds are
difficult to obtain.
The global infrasonic array network has an intra-station spacing of 2200
km. Although each array comprises several microbarometers that permit
one to pinpoint the direction from which infrasonic waves originate, the
large intra-station spacing makes it impossible to study the finer
details of how infrasonic ray paths move through atmospheric structure.
The 70-km intra-station spacing of the USArray, either using
seismometers or microphones, allows one to investigate these details in
unprecedented spatial resolution.
In this presentation, I aim to briefly discuss infrasonic sources,
propagation physics, and reception. I will then focus on recent UCSD
studies of infrasound and gravity waves using USArray seismometers and
microphones. I will briefly discuss the potential of using USArray
seismometers and microphones in joint studies of sources of opposing
oceanic waves. Lastly, I will conclude with a list of needed things to
facilitate future infrasonics research and improve the ability of the
infrasonics community to grow.
Required: Windows® 7, Vista, XP or 2003 Server
Required: Mac OS® X 10.5 or newer
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