Groundwater resources play an increasingly crucial role in providing the water required to sustain the environment. However, our understanding of the state of surficial aquifers and their spatiotemporal dynamics remains poor. In this study, we demonstrate how Rayleigh wave velocity variation can be used as a direct indicator of changes in the water level of a surficial aquifer in a discontinuous permafrost environment.
Wednesday, October 11, 2023
Craft Republic Houston • 11470 Westheimer Rd.
Social 5:30 p.m., Dinner 6:30 p.m., Presentation 7:30- 9:00 p.m.
Cost: $35 for Pre-registered members; $40 for non-members & ALL walk-ups. Students: $15
To guarantee a seat, you must pre-register on the HGS website and pay with a credit card. You may walk up and pay at the door if extra seats are available. Please cancel by phone or email within 24 hours before the event for a refund. Online & pre-registration closes Wednesday, 10/11/23, at 5:00 a.m.
Monitoring Water Level of a Surficial Aquifer Using Distributed Acoustic Sensing and Ballistic Surface Waves
Speaker Valeriia Sobolevskaia , Rice University
Groundwater resources play an increasingly crucial role in providing the water required to sustain the environment. However, our understanding of the state of surficial aquifers and their spatiotemporal dynamics remains poor. In this study, we demonstrate how Rayleigh wave velocity variation can be used as a direct indicator of changes in the water level of a surficial aquifer in a discontinuous permafrost environment. Distributed acoustic sensing (DAS) data, collected on a trenched fiber-optic cable in Fairbanks, AK, was processed using the multichannel analysis of surface waves (MASW) approach to obtain temporal velocity variations. A semi-permanent Surface Orbital Vibrator (SOV) was utilized to provide a repeatable source of energy for monitoring. To understand the observed velocity perturbations, we developed a rock physics model representing the aquifer with the underlying permafrost and accounting for physical processes associated with water level change. Our analyses demonstrated a strong correlation between precipitation-driven head variation and seismic velocity changes at all recorded frequencies. The proposed model accurately predicted a recorded 3% velocity increase for each 0.5 m of head drop and indicated that the pore pressure effect accounted for approximately 90% of the observed velocity change. Surface wave inversion and sensitivity analysis suggested that the high velocity contrast in the permafrost table shifts the surface wave sensitivity toward the first 3 m of soil where hydrological forcing occurs. This case study demonstrates how surface wave analysis combined with a rock physics model can be used for quantitative interpretation of the acoustic response of surficial aquifers.
About the Speaker:
I am a geophysicist with oil and gas background who is now working on hydrogeologic problems. I got my BSc in Geology from St Petersburg State University, Russia in 2012 and a MSc degree in Reservoir Management from Herriot Watt University, UK in 2014. After that I joined ExxonMobil and spent 4 years working in Russia and Houston, TX in a variety of different projects from early exploration to production. Long story short, at some point I decided to continue my education and went first to UT Austin where I got another MSc degree. Currently I am at Rice University pursuing a PhD degree in Geophysics. I am working with Dr. Jonathan Ajo-Franklin in his Rice Environmental and Applied Geophysics Lab with a primary focus of understanding aquifer behavior using geophysics.
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