Colorado Association of Geotechnical Engineers - Event Information

Event Name:CAGE/SEAC Breakfast - Seismic Surveys

Seismic Surveys for Vs30 IBC Seismic Site Classification
and Denver-Metro Measurements

Phil Sirles, MS - Senior Geophysicist/Operations Manager - Collier Geophysics, LLC
1 PDH 

Seismic investigations have been used in resource exploration since the early 1900’s, however they were not used for engineering projects until the late 1970’s. Their use started gaining prominence in 1984 with the first ASTM test standard for any geophysical test. The Uniform Building Code (UBC) furthered the use of measuring in-situ P- and S-wave velocities on a site-specific basis domestically; and now, its application has become routine through specifications in the International Building Code (IBC), first released in 2000. Drilling and SPT N-values remain as the primary approach used by engineers for IBC site classification, but in the last decade a few advancements in the geophysical industry have allowed seismic investigations to confirm, and support drilling results using fewer and shallow(er) borings to derive the seismic site classification. The presentation will discuss the progression of seismic methods for engineering use, with emphasis on site classification as specified by the IBC standard. Determining a Vs30 value based on borehole and surface seismic methods will be explained as additional rational to apply these methods, particularly in cluttered urban settings. Using the Denver-Metro as an example, we will take a close look at where Vs30 values have been measured, and what the results mean on a broad scale to geotechnical engineers working with designers (at a metro-wide scale). In addition, a large-scale front range project where Vs30 and borehole data were acquired, will be compared and presented. Time permitting, a few other advancements illustrating the value of collecting these 1D Vs30, or 2D Vp & Vs seismic profiles, or 3D volumetric measurements to characterize the subsurface for engineering design needs will conclude the presentation.
Mr. Sirles received his bachelors in Geology in 1980 at Fort Lewis College, Durango, CO; and masters in Geophysics in 1985 from Mackay School of Mines - Univ. Nevada-Reno. Phil is Collier’s Operations Manager (for western operations), Sr. Geophysicist and Business Development Manager. Phil proclaims himself as an engineering geologist using geophysics to help clients solve geologic, hydrologic and engineering problems. He stared his career with 10 years at the Bureau of Reclamation, and has been a consultant for 26 years, a total of 36 as of January 2022!
Something he is quite proud of is that for the last two decade he helped Central Federal Lands of FHWA to complete a series of books, publications, a technical website, and a set of training DVDs’ as instructional materials on “The Application of Geophysics for Transportation Projects”. Because he enjoys working with- and educating geologists and engineers how to apply the correct use of geophysics to address their project objective(s), he became accredited by the International Association for Continuing Education and Training. Since then he has taught and continues to provide short courses for FHWA, state DOT’s, ASCE, AEG, EEGS, the ACSM.  
In 2000, he was President of the Engineering and Environmental Geophysics Society; 2016, he served as the Chair for the Near-Surface Geophysics Technical Section of the Society of Exploration Geophysicists (SEG is the worlds largest geophysics society); and, currently sits on the North American Regional Advisory Council (RAMAC) for SEG.
He has conducted engineering geophysical investigations domestically in 46 of 50 states, and internationally in 6 countries.  He has authored over 60 papers on a variety of subjects.  He is a proud Colorado Native, but much more proud to point out locations throughout Colorado where he scrambled hill-and-dale to acquire geophysical data for various projects!
Event Date:1/20/2022
Event Time:7:30 AM - 9:00 AM Mountain
Location:Doubletree Westminster
8773 Yates Dr.
Westminster, CO

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