Research Page

My Research Interests:
Earth Science, Human/Environmental Interactions, Education

Home Mentoring, Teaching, and Philosophy Background and CV Photos My Weblinks

Ongoing and Evolving Research Topics

Tectonic Geomorphology
and Earthquake Geology

Urban
Geosciences

Environmental Justice
and Earthquake Hazards

Geoscience Ed and
Interdiscplinarity

Other
Research Interests

Earthquake Geology and Tectonic Geomorphology
I am broadly interested in fundamental questions about fault zone structure, interactions between tectonics and landscape development, and earthquake hazards. I study these topics using the tools of paleoseismology, geomorphic and fault zone mapping, and analyses of historical data. I have been focusing my research on the Parkfield segment of the San Andreas Fault (SAF). Parkfield is interesting because of its historical patterns of strain release including recurring moderate magniture earthquakes that rupture multiple surface traces of the SAF, spatially-variable aseismic fault creep, and its position relative to the great 1857 Fort Tejon Earthquake. Additionally, Parkfield has been the subject of much geophysical earthquake science for comparison to the geomorphic/structural mapping and paleoseismic investigations we have been conducting. In addition to my research at Parkfield I have been involved in Paleoseismic investigations along the Carrizo Segment of the SAF and have participated in tectonic geomorphic mapping and paleoseismic investigations in Baja California Sur.

The Parkfield Segment of the San Andreas Fault

This research stems from my Masters thesis and an NSF EAR-Tectonics written by Ramon. Fortunately with the help of a NEHRP grant the research has carried on into my dissertation. Here is a copy of my Master's Thesis titled: Paleoseismology, Slip Budget, and Fault Behavior Along the Parkfield Segment of the San Andreas Fault (SAF)

Additionally, I contributed to three papers to the Bulletin of the Seismological Society of America's special issue on the 2004 M6.0 Parkfield Earthquake. Below I provide links to these papers and related presentations and information.

Slip Budget and Earthquake Hazard
In this paper I review geodetic studies and earthquake rupture mapping reports by numerous other SAF earthquake scientists to perform an analysis of slip budget for Parkfield and to place our paleoseismic research into context:
Toké, N.A., J R. Arrowsmith, (2006) Reassessment of a slip budget along the Parkfield segment of the San Andreas Fault, Bulletin of the Seismological Society of America, v. 96, 339-348.

We also presented a poster on this slip budget at the 2005 annual SCEC Meeting
Toké, N.A. and Arrowsmith, J R. "Estimating a Slip Budget along the Parkfield segment of the San Andreas Fault: A Slip Deficit since 1857" Southern California Earthquake Center Annual Meeting, Proceedings and Abstract, vol. 15. 2005

Mapping of the 2004 Earthquake
Ramon and I mapped some of the 2004 Earthquake rupture and after slip. We focused especially on Middle Mountain and a detailed Total Station survey of the Miller's Field Paleoseismic Site. We shared our information with Michael Rymer and other USGS colleagues; contributing to the following publication.
Rymer et al., 2006: Surface Slip Associated with the 2004 Parkfield, California Earthquake. Bulletin of the Seismological Society of America, V 96, p. 11-27.

Here is a map of the 2004 rupture pattern at the Miller's field Paleoseismic site!

The imagery is from the B4 LiDAR with our 2004 and 2007 paleoseismic trenches (black; about 1-2m wide) overlain by the 2004 earthquake fractures (red).

Paleoseismology and Earthquake Geology
We also published our 2004 Paleoseismic Results in the 2006 special BSSA issue: Toké et al., (2006) Paleoseismic and Post Seismic observations of Surface Slip along the Parkfield sement of the San Andreas Fault, Bulletin of the Seismological Society of America, v. 96, 221-238.

We presented a couple posters leading up to this publication:

Toke, N.A., Arrowsmith, J R., Crosby, C.J., and Young, J.J. “Paleoseismology and Tectonic Geomorphology: Results from the Parkfield, CA Segment of the San Andreas Fault.” EOS Trans. AGU, 85 (47), Fall Meet. Suppl., Abstract T13A 1336, 2004.

Rymer, M.J., Tinsley, J.A., Treiman, J.A., Arrowsmith, J R., Clahan, K.B., Rosinski, A., Fuis, G.S., Bryant, W.A., Branum, D.M., Snyder, H.A., Toke, N., Bawden, G.W., Devlin, S., 2004, Surface Slip Associated with the 2004 Parkfield, California, Earthquake, Eos Trans. AGU, 85 (47), Fall Meet. Suppl., Abstract S52D-08, 2004.

Toke, N.A., Arrowsmith, J R., Crosby, C.J., and Young, J.J. “Preliminary Paleoseismology Results from the Parkfield, CA Segment of the San Andreas Fault.” Southern California Earthquake Center Annual Meeting, Proceedings and Abstract, vol. 14. 2004.

In 2007 we returned to Parkfield thanks to a NEHRP Grant. Here is the Final Technical Report.
We opened several trenches along the Southwest Fracture Zone, however, there was no interpretable stratigraphy because of severe bioturbation. We returned to the 2004 Miller's Field site, logged three new trenches and collected additional radiocarbon samples that were partially funded by SCEC. By dating the timing of the sag pond's scarp formation we were able to estimate a late Holocene slip rate from the right-laterally offset stream at the Miller's field site. This slip-rate is for the main SAF trace only. We are preparing a publication discussing this slip rate and the additional paleoseismic data (checkback soon!)

Prior to our 2007 field season we presented a poster considering sites for slip-rate investigation at SCEC:

Toké, N.A. and J R. Arrowsmith “Paleoseismic and Holocene slip rate investigations along the San Andreas Fault, at Parkfield, California” Annual Southern California Earthquake Center meeting, September 9-12th, 2007, Palm Springs, CA.

We have now presented three additional posters on the results

2007 AGU: was right after the field season this poster presents some very preliminary in our interpretations.
Toké, N.A. and J R. Arrowsmith “Paleoseismic and Holocene slip rate investigations along the San Andreas Fault, at Parkfield, California” EOS Transactions American Geophysical Union, Fall Meeting, December 13th, 2007 Abstract: T43A-1097.

2008 AGU: here we begin to explore the idea of calculating a slip rate from the sag pond's age.

Toke, N. A., J R. Arrowsmith, M. Rymer, A. Landgraf, J. Coyan, M. Busch, D. Haddad Paleoseismic interpretation and a preliminary geologic slip rate for the Parkfield segment of the San Andreas Fault, Eos Transactions. American Geophysical Union, 89(52), Fall Meeting, December 15-19th 2008, Abstract T41A-1955.

2009 SCEC: now we are just about ready to submit a paper discussing this slip-rate calcuation.

Toke, N. A., J.R. Arrowsmith, M.J. Rymer, A. Landgraf, J. Coyan, M. Busch, D . Haddad “Long-lived creep, M6 earthquakes, and a Holocene slip rate for the main trace of the San Andreas Fault at Parkfield, California” Annual Southern California Earthquake Center meeting, September 12-16th, 2009, Palm Springs, CA.

Additional Earthquake Geology an Tectonic Geomorphology Research:

Earthquake Geology of the Carrizo Plain

In the summers of 2004-2006 I helped on field campaigns in the Carrizo Plain that were led by Sinan Akciz, Lisa Grant, Gabriela Noriega, and Ramon Arrowsmith, but included many other colleagues. Here are some examples of the ideas that have emerged from that research. These abstracts are just a teaser as they have since taken this research much futher in collaboration with Olaf Zielke's B4 LiDAR Mapping of the Carrizo. It seems as though they will soon have some significant papers coming to light.

Akciz, S.O., L.B. Grant, J R. Arrowsmith, O. Zielke, N.A. Toke, G. Noriega, J. Cornoyor, E. Starke, N. Reusseau, B. Campbell “Does the new paleoseismological evidence from the Carrizo Plain section of the San Andreas Fault indicate abnormally high late Holocene slip rates?” EOS Transactions American Geophysical Union, December 11-15th 2006, Fall Meeting, Abstract: T21E-01.

Akciz, S., L.B. Grant, J R. Arrowsmith, O. Zielke, N.A. Toke, G. Noriega, E. Starke, and J. Cornoyer. “Constraints on ruptures along the San Andreas Fault in the Carrizo Plain: Initial Results from 2005 Bidart Fan Site Excavations.” Southern California Earthquake Center Annual Meeting, Proceedings and Abstracts, vol. 15. September 11-14th, 2005

Tectonic Geomorphology and rifting of Southern Baja California
In the spring of 2006 I helped organize a field campaign to Baja California Sur with colleagues from here at ASU, NAU, as well as Mexico. Melanie Busch has taken the lead on this work since that time and has been working towards some interesting results. Some of the initial data can be viewed on our Active Tectonics Group Webpage under the research on Neotectonics Across an Active Oblique-Divergent Plate Margin, Southwestern Gulf of California

I was also a coauthor on Melanie's 2006 AGU abstract: Busch, M., J R. Arrowsmith, P.J. Umhoefer, G.M. Gutierrez, N. Toke, D. Brothers, E. Dimaggio, S. Maloney, O. Zielke, B. Buchanan “Late Quaternary Faulting in the Cabo San Lucas – La Paz region, Baja California.” EOS Transactions American Geophysical Union, Fall Meeting, December 11-15th 2006, Abstract: T41D-1612

Tectonic Influences on Topography in New Zealand
The most formative of my research experiences with Active Tectonics was inn the fall of 2001 and spring of 2002 when Keith Klepeis introduced me to GIS and active tectonics. We used a 30m digital elevation model of New Zealand to explore relationships between regions of uplift, climate, and the Alpine fault system in southwestern New Zealand. We discovered a large region of uplift that was geographically separated from climate-driven uplift and geographically linked to oblique-slip motion along the convergence of several faults of the Alpine fault system.

Here are the abstracts on which I was a contributor:

Klepeis, K.A., Clarke, G.L., and *Toke, N., “Exhumation and Topographic Uplift along Continental Strike-Slip and Oblique-Slip Faults in Southwest New Zealand.” GSA Abstracts Vol. 35, No. 6, 2003.

Toke, N.A. “Tectonics and Topography: Some New Relationships Identified along the Alpine Fault in New Zealand”, Vermont Geological Society Newsletter, spring 2002.

Klepeis, K.A., Claypool, A., and *Toke, N., “Dynamic topography in transpressional regimes: an example from the New Zealand plate boundary zone.” GSA Abstracts Vol. 34, No. 1, 2002

Urban Geology, Geomorphology and Hydrology

My interests in the human role in altering earth surface processes grew from my undergraduat thesis at the University of Vermont (see below). At Arizona State University I have been participating in our IGERT in Urban Ecology Fellowship program. Currently I am mentoring and collaborating with Laila El-Ashmawy (An undergraduate in Civil and Environmental Engineering) to study how humans alter sediment production in the urbanizing desert. We are working towards writing a paper for Geomorphology on the role of humans in changing hydrologic structure and sediment transport in desert urban environments.

Urbanization of the desert: Impacts on hydrologic structure and sediment transport.
Laila and I presented a 10 page manuscript, a talk, and a poster discussing the extremely low sediment production ratese we have estimated from urban neighborhoods in Tempe, AZ at the 2009 AHS meeting in Scottsdale, AZ.

Here is our paper: EL-Ashmawy, L., N.A. Toke, and JR. Arrowsmith "Geologic Investigations of Urban Sedimentation in Tempe, AZ Using Retention Structures." September, 2009 Arizona Hydrological Society Meeting, Scottsdale, AZ.

The accompanying talk given by Laila!

Finally, the co-presented poster:

and... an update to this research presented at the 2009 GSA Meeting (our abstract) and poster below:

I also collaborated with Rebecca Hale on a project probing hydrologic relationships in the urbanizing desert system of Phoenix, AZ. This work was stemming from our IGERT Urban Ecosystems Class with Nancy Grimm.
We presented at the 2008 CAP annual meeting:

My contribution to this project stemmed from an investigation of downstream hydrology of Indian Bend Wash watershed in Scottsdale and Tempe, AZ. THis analysis showed that urbanization had significantly alterned hydrology. Downstream hydrographs and total runoff typically decreased, however at the end of the system runoff spiked. This is a prime example of the complexities in rerouting hydrology in the urban system. Underlying this are many Engineering decisions as well as unintended effects. Certainly the result has impacts on the urban ecosystem.

Here are two posters stemming from this investigation:
2007 CAP Symposium:

2006 Binghamton Symposium on the Human Role in Changing Fluvial Systems. Here is a very interesting Geomorphology volume associated with that Symposia.

Relationships between Greenspace compaction and urban hydrology in Burlington, VT

Much of my interest in the human role in altering hydrology and geomorphology in urban environments stems from my Undergraduate John Dewey Honors thesis at the University of Vermont. My mentor for this project was Dr. Paul Bierman and there were many other research collaborators: Jackie Hickerson, Megan McGee, Lyman Persico (a fellow Peoples Academy Alum), Dr. Kyle Nichols, Paul Melillo and Jim Kurfis studying physical and chemical effects of Greenspace loss in relation Stormwater hydrology in Burlington, VT. Our research effort was called Urban Hydrology and Landuse Change Over Time in Burlingon, VT.

SUMMARY: Kurfis, Bierman, and Nichols made the observation that Burlington had lost a large percentage of highly permeable greenspace due to single family residences being converted into multi-apartment housing, primarily used by off campus college students. Mellilo, Bierman, McGee, Hickerson and I tested the effects of greenspace loss on runoff quantity using a simulated rainfall tests on plots with varrying levels of greenspace "health". It was obvious that as a result of greenspace loss storm water runoff was dramatically increased. Bierman, Persico and I set up two temporary weirs in two small drainage basins (one residential, one slightly more urban) to measure stormwater flow and collect water samples for chemical analysis. The results showed that increased storm water runoff carried a variety of pollutents. Mcgee, Bierman, Persico, Hickerson and I tested how to best remediate lost greenspace using a variety of methods and statistical analysis. Hickerson led an effort to inform the community of the issue at hand and was successful in bringing the problem of lost greenspace into community dialogue through use of the media (TV and Newspaper). This topic is of ongoing debate and concern in Burlington as the residents take pride in their beautiful city and waterfront.

Here is the manuscript (PDF) of my undergraduate thesis which addresses all of the above issues; I am currently working on a manuscript for publication of this work focusing on the greenspace remediation aspects of this work:

Toke, Nathan A. “Compacted green space and effects on storm water hydrogeology in Burlington, Vermont.” University of Vermont John Dewey Honors Thesis, 2003.

Environmental Justice and Geology

I am looking at the relationship between different types of earthquake hazards in California and relating hazard to demographics and historical context to begin to understand how certain populations are exposed differently to earthquake hazards and how this risk came to be inequitable. The work is in its formative stages so check back later for updates!

Educational Research

Working with graduate students and faculty from across 4 different programs at ASU we have been looking at how student and instructor goals and preceptions of interdisicplinary education meet. Out model has been to study faculty and students from the Schools of SOS, SHESC, and SOLS here at ASU who are involved in Interdisciplinary undergraduate Courses at the 300-400 level. We interviewed 20 faculty, surveyed all of their students and selected students to participate in focus groups. We are now finishing up processing/analyzing this qualitative data. It turns out that qualitative analysis is quite nuanced and time consuming (I learned). Check back soon for links to more publications stemming from this research (a paper we hope), but for now here are a couple of abstracts and meeting presentations.

I presented some of the results from this study in the Geoscience Education section of the 2009 GSA annual Meeting in Portland, OR.
Please read through the poster for some of the major results.

Kate Darby also presented some of our results at the 2009 AESS meeting (Association for Environmental Studies and Sciences) in Madison Wisconsin.
Her talk was titled "Challenges in the classroom: reconciling student and instructor perspectives on interdisciplinary courses."

Additional Research Involvement

Geological Relationships between the Little Chazy River, NY and the Geology of Altona Flat Rock and the Surrounding Area.

During the summer of 2002 I had a wonderful opportunity to explore my interests in surficial hydrogeology through an REU fellowship (NSF research experience for undergraduates). The program was run through Plattsburgh State University of New York and headed by Dr. David Franzi. I also worked closely with the following people: Edwin Romanowicz, Susan Billow, Michael Krasilovsky, and Julie Rimbault.

Here is the abstract on which I was a contributor:

Billow, S., Krasilovsky, M., Rimbault, J., *Toke, N., Romanowicz, E.A, and Franzi, D.A. “A preliminary hydrogeochemical assessment of the Little Chazy River, northeastern New York” Geological Society of America Abstracts with Programs, V.35, No.1, 2003.

Lake Evolution and Paleoclimatology/Hydrology
During the summer of 2001 I worked with Dr. Andrea Lini and his graduate student Andrea Lord as a research assistant. I assisted in the collection of deep-lake shallow-sediment cores. These cores were taken because deeper-cores taken during previous winter-collection do not preserve the shallow sediments. These cores were used to study the evolution of lakes in Northern New England (USA) since the last ice age. I also worked in Andrea's isotope lab as a gas-line separation technician and running his mass spec for delta 13C measurements. The results of this work were very interesting documenting periods of storminess and the comeback of biota to the landscape after the last ice age.

Here are the abstracts on which I was a contributor:

Lord, A., Lini, A., *Toke, N., Parris, A., and Bierman, P. “Contrasting evolution of northern New England post-glacial lakes.” GSA Abstracts, Vol. 34, No. 1, 2002.

Lord, A., Lini, A., *Toke, N., Parris, A., and Bierman, P. “Post-glacial evolution of northern New England lakes.” GSA Abstracts, Vol. 33, No. 6, 2001.

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