I. INTRODUCTION This fieldwork was done last November 11, 2012, Sunday at Greenwoods Executive Village, Pinagbuhatan, Pasig City. Two (2) students under the tutelage of Dr. Arturo S. Daag joined a group of scientist from PHIVOLCS in conducting Refraction microtremor survey at two (2) designated areas inside the village. Refraction microtremor (ReMi) is a surface-performed geophysical survey developed by Dr. John Louie (and others) based on previously existing principles of evaluating surface waves and in particular Rayleigh waves. The refraction microtremor technology was developed at the University of Nevada and is owned by the State of Nevada. Optim of Reno, Nevada has the exclusive license to develop the technology, and SeisOpt® ReMi™ has been available commercially from Optim since 2004. Since Rayleigh waves are dispersive, the propagating waves are measured along a linear seismic array and evaluated relative to wave frequency and slowness (or the inverse of the velocity). Due to the dispersive characteristics of higher frequency waves travelling through the more shallow conditions and lower frequency waves passing through deeper materials, a 1-D sub- surface profile can be generated based on the velocity with depth. ReMi is a new, proven seismic method for measuring in-situ shear-wave (S-wave) velocity profiles. It is economic both in terms of cost and time. Testing is performed at the surface using the same conventional seismograph and vertical P-wave geophones used for refraction studies. The seismic source consists of ambient seismic "noise", or microtremors, which are constantly being generated by cultural and natural noise. Because conventional seismic equipment is used to record data, and ambient noise is used as a seismic source, the ReMi method is less costly, faster and more convenient than borehole methods and other surface seismic methods, such as SASW and MASW used to determine shear-wave profiles. Depending on the material properties of the subsurface, ReMi can determine shear wave velocities down to a minimum of 40 meters (130 feet) and a maximum of 100 meters (300 feet) depth. ReMi can be used to obtain Vs profiles for: Earthquake site response, Liquefaction analysis, Soil compaction control, Mapping the subsurface and estimating the strength of subsurface materials, Finding buried cultural features, such as dumps and piers and Offshore surveys to determine depth to bedrock for harbor and pier extensions.
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Transcript
I. INTRODUCTION
This fieldwork was done last November 11, 2012, Sunday at Greenwoods Executive Village,
Pinagbuhatan, Pasig City. Two (2) students under the tutelage of Dr. Arturo S. Daag joined a group
of scientist from PHIVOLCS in conducting Refraction microtremor survey at two (2) designated
areas inside the village.
Refraction microtremor (ReMi) is a surface-performed geophysical survey developed by
Dr. John Louie (and others) based on previously existing principles of evaluating surface waves and
in particular Rayleigh waves. The refraction microtremor technology was developed at the
University of Nevada and is owned by the State of Nevada. Optim of Reno, Nevada has the exclusive
license to develop the technology, and SeisOpt® ReMi™ has been available commercially from
Optim since 2004. Since Rayleigh waves are dispersive, the propagating waves are measured along
a linear seismic array and evaluated relative to wave frequency and slowness (or the inverse of the
velocity). Due to the dispersive characteristics of higher frequency waves travelling through the
more shallow conditions and lower frequency waves passing through deeper materials, a 1-D sub-
surface profile can be generated based on the velocity with depth.
ReMi is a new, proven seismic method for measuring in-situ shear-wave (S-wave) velocity
profiles. It is economic both in terms of cost and time. Testing is performed at the surface using the
same conventional seismograph and vertical P-wave geophones used for refraction studies. The
seismic source consists of ambient seismic "noise", or microtremors, which are constantly being
generated by cultural and natural noise. Because conventional seismic equipment is used to record
data, and ambient noise is used as a seismic source, the ReMi method is less costly, faster and more
convenient than borehole methods and other surface seismic methods, such as SASW and MASW
used to determine shear-wave profiles. Depending on the material properties of the subsurface,
ReMi can determine shear wave velocities down to a minimum of 40 meters (130 feet) and a
maximum of 100 meters (300 feet) depth.
ReMi can be used to obtain Vs profiles for: Earthquake site response, Liquefaction analysis,
Soil compaction control, Mapping the subsurface and estimating the strength of subsurface
materials, Finding buried cultural features, such as dumps and piers and Offshore surveys to
determine depth to bedrock for harbor and pier extensions.