Refraction Microtremor (ReMi) for Shear Velocity
July 18, 2005
John Louie of the
CEMAT project at the
Nevada Seismological Lab
radically new and simple way to estimate shear velocity in-situ to
depths as great as 100 meters (300 ft).
Louie's team at UNR has measured more than 400 sites in the last 4 years.
The Most Efficient Shallow Shear-Velocity Estimates
Optim LLC, a Nevada software
developer, has released a full desktop ReMi analysis and modeling
package. SeisOpt®ReMiTM technology
has been licensed to dozens of geotechnical consultants and agencies.
Per-site and unlimited licenses are available. Please contact
email@example.com for more information.
You simply record noise from your site, on your existing
seismic refraction gear. With no seismic source required, you can
collect good data at the noisiest urban sites using two person-hours
or less. It is now possible to get a quality shear-wave assessment of
shallow earthquake site effects in just a few hours, at one-tenth the
cost of a logged borehole.
Step One: Fast, Easy Data Collection
All you need is 24-channel digital refraction gear with 8-to-12 Hz single
phones. Put the cable across your site in a line 200 m (600 ft)
long, with about 8 m (25 ft) spacing between phones. Take 3 to 10
records of background noise, 20-60 seconds long each. That's it!
You might be able to measure four sites in one 8-hour shift.
Shear-velocity analysis of other types of data-collection geometries
and other types of records can still work. (Multi-phone reflection
groups and stacked hammer records probably won't.)
Read all about it in the ReMi Field
Step Two: Send Your Data Files
A commercial data-analysis package was released by
Optim LLC in June 2002.
To have us evaluate your data, please contact
Please specify your own
contact information, as well as the spacing between the geophones and
the time sampling interval, for double-checking. Data files in SEG-2,
SEG-Y, or SEG-D are easiest to work with; contact us for other
Copyright © 2003 John N. Louie