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About John Jasbinsek: I am a geophysicist kept off the street by the Physics Department at California Polytechnic State University, San Luis Obispo.

If you are a student interested in a senior project or other independent study project please use the links above to see an overview of recent research projects.

Teaching


I regularly teach the following courses in geology and geophysics:

In Spring 2026 I will teach GEOL 305 Seismology and Earth Structure for the last time. This course is ending because starting in Fall 2026 Cal Poly is moving to the semester system and there is simply not as many opportunities to teach different courses.

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Cal Poly Geology


Cal Poly offers a complete course of study in geology via the Geology Concentration within the Environmental Earth and Soil Science B.S. degree program.

The Geology Concentration satisfies the educational requirements needed for the Professional Geologist license in California. Please see the Cal Poly Geology website for much more detailed information.

The Geology Concentration will also allow you to pursue graduate studies in geology and most any other area of the earth sciences.

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Geophysical Research at Cal Poly San Luis Obispo


I work in a supervise student research projects (i.e. independent study, senior projects, or just hanging around a field project) in the two primary areas outlined below.

If you are a student interested in one of the topics below, or want to get me interested in some other topic (which isn't difficult), please email me or drop by my office sometime.

Near-surface geophysics applied to hydrogeology

I collect near-surface geophysical data (electrical resistivity and seismic methods) to image subsurface structures (e.g. layering, folding, faults) with the goal of understanding the distribution and movement of groundwater.

Lately we have been working in an exposure of weathered Salinian Block granite in Paso Robles, CA. We successfully interpreted a number of electrical resistivity tomography profiles that were collected to detect where the permeable fractured granite exists.

The landowner drilled an exploratory groundwater well based on our recommendation and it wa successful, yielding almost 50 gallons per minute, which is on the high side in such terrains.

The vertical well shows that with depth the yield increases from none, to 20 gpm, to 50 gpm.

Much more work at this field site as well as other exposures of weather Salinian Block granite (for example, in Santa Margarita, CA) is ongoing/planned. It may be possible to make estimates of hydraulic parameters (e.g. hydraulic conductivity) using electrical resistivity and induced polarization imaging (Revil and Florsch 2010).

Aside from the geophysical imaging, it is possible to think about determining the isotopic groundwater age in the permeable fractured layer and the recharge through the saprolitic weathered layer.

References

Revil, A., and N. Florsch, 2010, Determination of permeability from spectral induced polarization in granular media, Geophysical Journal International, doi: 10.1111/j.1365-246X.2010.04573.x.

Global Seismology

Global seismology analyzes earthquake waves to infer/constrain the earth’s deep interior structure and state.

Ultra-low Velocity Zones (ULVZ) at the Core-mantle Boundary

Recently students have been exploring ultra-low velocity zones (ULVZ) at earth’s core-mantle boundary at 2,900 km depth using PcP and ScP seismic phases. Read an overview of ultralow low velocity zones (Yu and Garnero 2018). Here is a really nice study of ULVZ and ScP waveform modeling (Rost and Revenaugh 2003).

The image below shows a model fit (red: data, blue: synthetic) of ultra-low velocity zone structure using PcP phase arrivals recorded at a high density array.

The PcP phase arrival shows an ultra-low velocity zone structure at the core-mantle boundary. The best fitting one-dimensional ULVZ model has a thickness of 6.5 km and S-wave velocity decrement of 27.5%.

Interestingly, no density increase or P-wave velocity decrement is needed; in fact, increasing the density and/or decreasing P-wave velocity immediately begins to degrade model fit - with the important caveat that these are only one-dimensional models.



References

Rost, S., and J. Revenaugh, 2003, Small-scale ultralow-velocity zone structure imaged by ScP, Journal of Geophysical Research: Solid Earth, 108, no. B1, doi: 10.1029/2001JB001627.

Yu, S., and E. J. Garnero, 2018, Ultralow Velocity Zone Locations: A Global Assessment, Geochem Geophys Geosyst, 19, no. 2, 396–414, doi: 10.1002/2017GC007281.

Core-rigidity Zones

Students are also modeling ScP waves for anomalous structure at the core-mantle boundary. The image below shows a stack (linear and phase-weighted) of P-waves and ScP-waves. The ScP response is suggestive of a core-rigidity zone (CRZ) structure (Rost and Revenaugh 2001), or → direct link to PDF.

Some observations of a CRZ structure were also detected with ultra-low velocity zone (ULVZ) observations (Rost and Revenaugh 2003) → freely downloadable from Journal of Geophysical Research.

The above two references are the only previous CRZ observations in the literature I am aware of.

References

Rost, S., and J. Revenaugh, 2001, Seismic Detection of Rigid Zones at the Top of the Core, Science, 294, no. 5548, 1911–1914, doi: 10.1126/science.1065617.

Rost, S., and J. Revenaugh, 2003, Small-scale ultralow-velocity zone structure imaged by ScP, Journal of Geophysical Research: Solid Earth, 108, no. B1, doi: 10.1029/2001JB001627.

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Photo Albums


Course (and maybe eventually field research) photo albums.

Applied Geophysics (GEOL 420)

Fall 2024   Fall 2023   Fall 2022   Fall 2021  
Fall 2020   Fall 2019   Fall 2018   Fall 2017  
Fall 2016   Fall 2015   Fall 2014

Seismology & Earth Structure (GEOL 305)

Spring 2024   Spring 2022   Winter 2020   Winter 2018  
Fall 2015

Physical Geology Laboratory (GEOL 241)

Spring 2023   Spring 2021   Winter 2021   Spring 2019  
Spring 2018   Spring 2017  

Geologic Excursions (GEOL 206)

Winter 2024   Fall 2021   Spring 2019   Spring 2018  
Fall 2016  

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