Project Aim:
With this study, I intend to advance our understanding of how flowing water in rivers produces seismic noise. I will focus on current knowledge gaps in this field and evaluate the underlying assumptions behind a priori models of seismic noise generation. This study will also monitor bedrock channeled river, which is unrepresented in the literature.
Why would NSF Care?
According to the Geomorphology and Land Use Dynamics solicitation, NSF is interested in the relationship between humans and geomorphology.
With remote seismic methods to evaluate flow velocity, we can improve river monitoring, erosion modeling, and data quality in fluvial geomorphology, which will lead to safer river management. Geomorphologists who study floods and erosion are limited in their ability to monitor rivers in flood, due to physically hazardous conditions. Even under normal flow conditions, direct in-channel measurements of flow velocity are time-consuming and difficult.
The study area is in an urbanized environment along the Atlantic Fall Zone. Urbanization leads to more intense flooding via increased runoff. The Oroville Dam crisis is a recent and interesting natural laboratory.
Background:
As rivers flow, they produce ground vibrations from a variety of sources. To date most research has focused on quantifying bedload transport events during floods (1), the monsoon season (2), dam removals (3), and physical dumping of bedload into flowing rivers (4). Far fewer researchers have studied how flowing water generates surface seismic vibrations. Gimbert et al developed an a priori model to predict the total seismic power in the 1 - 100 Hz frequency band, but simplifying model assumptions limit its applicability to bedrock channels (5).
Unanswered Questions Raised by Previous Work:
1) What is the practical observation window of a seismometer along a river?
Methods to Evaluate: We will investigate the coherence of signals in an along-channel seismic array. If signals are highly coherent, they will not be fully independent measures.
Methods to Evaluate: Deploy 3-component seismometers capable of 30-day continuous recording. Investigate the relationships between up-down, north-south, and east-west motions. Use data collected near Oroville Dam as a natural experiment.
3) What is the source of seismic energy released from flowing water? Is it related primarily boundary roughness resistance, or internal distortion resistance?
Methods to evaluate: Investigate relationships between roughness (grain size or bedrock roughness metric), turbulence (via Reynold's number), and 3-component response within observation reaches. Use flume scale models for preliminary evaluation.
4) Is seismic energy released appreciably different between similarly sized bedrock and alluvial systems?
Methods to evaluate: Simultaneous deployment 3-component nodes within of bedrock and alluvial reaches of the same river. Conduct active source characterization of along-channel material.
5) Is cavitation a significant contribution to the acoustic and seismic outputs of rivers under the conditions predicted by Barnes (1956) and Whipple et al. (2000) (7,8)?
Methods to evaluate: Remote deployment of in-stream hydrophone and seismometer under conditions when cavitation is predicted. A the non-linear onset of high frequency (~20 kHz) acoustic noise matching laboratory cavitation will indicate the presence of cavitation.
Sources:
1- Burtin, A., L. Bollinger, J. Vergne,
R. Cattin, and J. L. Nábělek (2008), Spectral analysis of seismic noise induced
by rivers: A new tool to monitor spatiotemporal changes in stream
hydrodynamics, J. Geophys. Res., 113, B05301, doi:10.1029/2007JB005034.
2- Chao, W.A., Wu, Y.M., Zhao, L., Tsai, V.C., and Chen, C.H., 2015, Seismologically determined bedload flux during the typhoon season: Scientific Reports, v. 5, 8261, doi: 10 .1038 /srep08261.
3- Schmandt, B., Aster, R.C., Scherler, D., Tsai, V.C., and Karlstrom, K., 2013, Multiple fluvial processes detected by riverside seismic and infrasound monitoring of a controlled flood in the Grand Canyon: Geology, p. 4858–4863, doi: 10 .1002 /grl .50953.
3- Schmandt, B., Gaeuman, R.C., Stewart, R., Tsai, V.C., and Smith, J., 2017, Seismic array constraints on reach-scale bedload transport: Geophysical Research Letters, v. 40, p. 4858–4863, doi: 10 .1002 /grl .50953. doi: 10.1130/G38639.1
5- Gimbert,
F., Tsai, V.C., Lamb, M.P., 2014, A physical model for seismic noise generation
by turbulent flow in rivers, JGR-Earth Surface
7- Barnes, H.L., 1956, Cavitation as a Geological Agent: American Journal of Science, v. 254, p. 493-505.
8- Whipple,
K. X., Hancock, G.S., and Anderson, R.S., 2000, River Incision into Bedrock:
Mechanics and Relative Efficacy of Plucking, Abrasion, and Cavitation: GSA
Bulletin, v. 112(3),
This is well thought out, easy to read and visually appealing. Since you can't do all of these, which projects are you leaning towards doing?
ReplyDeleteYour presentation was organized well but your figure of amplitude vs. outflow discharge is missing a colorbar. I like how you incorporate the Oroville dam to make your project more relevant to non-scientists.
ReplyDeleteThis is a very well thought-out idea, and presented in a very coherent way. Nice job, Phillip.
ReplyDeleteYou've obviously done a lot of thinking about these questions. However, for the sake of the presentation it would have helped if you have narrowed the scope. I realize that it may be early in the process for this, but it would have helped keep our attention. Another way to focus the presentation would be to frame each question within a larger overarching narrative so that things flow better and fit together.
ReplyDeleteI really like the structure of your proposal. You pointed out clearly why NFS would be interested in your project.Good presentation,
ReplyDeleteI like the second question you purpose. I think it might gain the most interest from a group of people concerned with how geomorphology can affect populations. Particularly, if you use a "natural disaster", i.e. the dam break to grab people's attention.
ReplyDeleteA bit long for an overview. Sounds like you have a few good possibilities for projects though.
ReplyDeleteWhat are your sample locations besides CA?
How realistic is it going to be to answer all of these questions in a single project? It seems like you move from development of a method to using it in a quite refined way.
ReplyDeleteGood to focus on proxy development for this acoustical technique, as applied to flooding. Proposal hopes to move field beyond the movement of bed load. Great to have explored the RFP to hone your project goals. What are you going to need (and what are the costs) for an array of seismometers? Fantastic to link the study to a recent failure of the Oroville Dam.
ReplyDeleteIt's a well-organized proposal but you have four potential projects for this proposal. Sometimes people may think you can't finish so much work in a proposal which may lower your probability to get the funding. You can just choose one or two of them for your proposal.
ReplyDeleteYou have good work here. Short but not lacking in quality. You do not give any reference when you mention something that has been done before early on. Agree with the previous statements about being too much work, at least without more information (participants, lengths, time-frame, etc.).
ReplyDelete