Dr. John Wakabayashi has been named the 2017-2018 Richard H. Jahns Distinguished Lecturer in Applied Geology.The Jahns Distinguished Lectureship, established in 1988, is sponsored by the Association of Environmental and Engineering Geologists and the GSA Engineering Geology Division. Its purpose is to provide funding for distinguished engineering geologists to present lectures at colleges and universities in order to increase awareness of students about careers in engineering geology. The lectureship is named in honor of Dr. Richard H. Jahns (1915- 1983), an engineering geologist who had a diverse and distinguished career in academia, consulting and government.
Biography
John Wakabayashi is a San Francisco Bay Area native who moved to Fresno in 2005 to begin his academic career as a geology professor at California State University, Fresno. He received his B.A. in Geology in 1980 from UC Berkeley, and his PhD in Geology in 1989 from UC Davis (advisor: Eldridge Moores). He is a Professional Geologist (California) and a Fellow of the Geological Society of America.
After graduating from Davis he worked as an engineering and environmental geologist for 16 years (1989-2005), the last 13 years as an independent consultant based in Hayward, California, before becoming an academic. He worked on a variety of different types of projects, including seismic hazard evaluation/paleoseismology, slope stability, engineering and forensic petrography, naturally occurring asbestos, and two Superfund projects on which his primary specialty was evaluation of ambient concentrations of metals of environmental concern in soils and rock. He was a member of the Working Group on California Earthquake Probabilities.
When not doing project work (ie. when not billable), he conducted independent research, some of which derived from his project work, but most of which dealt with more esoteric research issues such as subduction initiation processes, metamorphic P-T paths and metamorphic contrasts as tectonic indicators, emplacement of ophiolites, subduction interface processes and development of subduction complexes, evolution of orogenic belts, development of strike-slip fault systems, and long time and length scale geomorphology. He incorporated academic research of his own and others into all of his project work, trying to bridge the academic-applied geology gap from the standpoint of a practitioner. After becoming an academic he has continued his efforts to bridge this gap, with realization that the vast majority of geology professors have never been employed in the engineering and environmental geology profession that most geology graduates will work in. He incorporates both his professional and research experience into his teaching so as to better prepare students for professional careers, as well as providing a foundation for students who wish to undertake graduate study.
His research has resulted in 82 published papers and over 100 abstracts tied to presentations at major geoscience meetings. The breadth of his research has broadened rather than narrowed over time. In spite of the wide range of research interests, the geology of that beguiling train wreck of rocks known as the Franciscan Complex of coastal California remains his chief interest and the many aspects of mélanges have become his main focus since 2009. At Fresno State he teaches non-major introductory geology, geology major undergraduate courses in petrology, geomorphology, and structural geology, graduate courses on active tectonics/seismic hazard analysis and orogenic belt tectonics, and his bread-and-butter undergraduate course in advanced geologic field mapping (he makes his students map Franciscan along with landslides, flights of stream terraces and some potentially active faults). He has supervised or is supervising a large number of graduate and undergraduate student researchers, and this includes a number of students from outside of Fresno State.
Outside of geology and beer (an amateur brewer since 1994), he is probably best known for his experience trout fishing in the backcountry (must be hiked to) of California, having launched casts into over 750 different lakes, about 700 of these in the Sierra Nevada; 2015 was an especially good summer. His strength and fitness routine that prepares him for his fieldwork and recreational hiking (and burns off some of the beer), as well as holding his body together for his return to playing basketball, has also gained some notoriety. This routine includes excessively long plank sessions and multiple repetitions of muscle ups.
Abstracts
Dr. Wakabayashi will plan to have lectures related to:
- Insight into geologic mapping of mélanges from structural geologic research: Implications for engineering geologic analysis and illustration of the value of field geologic training.
With the continued decline in the amount and intensity of field training for geology students, researchers and young professionals are less well equipped to deal with the geologic complexity of mélanges than they were 10 to 20 years ago when they were already vexed. Detailed field work challenges the prevailing academic model of mélanges as mega shear zones (“subduction channels”) and shows that such mélanges formed as submarine landslide deposits. This leads to a significantly different model of processes along the subduction interface. It also has implications for practical mapping and characterization of mélanges for engineering purposes. A decade ago I had stated that the mode of mélange formation (sedimentary, diapiric, or tectonic) was not relevant to engineering characterization but I have shown this to be wrong, because different modes of formation make very different predictions for the distribution of materials and the nature of various contacts. The sad truth is mélanges are even more complex from a mapping standpoint than we had imagined a decade ago and this places a premium on geologic mapping skills and the training that builds such skills.
Based on the following published papers (but the applied geology implications are not in these papers):
Wakabayashi, J., 2017, Structural context and variation ocean plate stratigraphy, Franciscan Complex of California: Insight into mélange origins and subduction-accretion processes: Progress in Earth and Planetary Sciences 4: 18, 23p., doi: 10.1186/s40645-017-0132-y
Wakabayashi, J., 2015, Anatomy of a subduction complex: Architecture of the Franciscan Complex, California, at multiple length and time scales: International Geology Review, v. 57, p. 669-746. doi:10.1080/00206814.2014.998728.
- A field-based alternative to subduction channel models: Insight from mélange studies.
This is the more purely academic focused look at mélanges.
Mélanges are viewed by most in the research community as “subduction channels” that accommodate subduction interface slip across a very broad (kilometers of thickness) shear zone. The mixing of blocks of apparently disparate origin into matrix in this model is attributed to large-scale megathrust slip as well as “return flow” (direction of slip opposite to that of subduction). Detailed field studies indicate that so-called subduction channel mélanges are actually deformed sedimentary deposits, and that mixing of the blocks into matrix took place by submarine landsliding, which is a common phenomenon in large subduction zone earthquakes. Mélanges of this type are simply part of the sedimentary trench fill, and they are locally interbedded with “ordinary” turbidites. Matrix ranges from shaley to sandy and from siliciclastic to serpentinite with gradation and interfingering between these lithologies. Many high-pressure metamorphic blocks were previously metamorphosed and exposed on the surface prior to incorporation into the mélange and resubduction, and some blocks had two prior subduction-exposure cycles. Such histories are recorded in sand-size grains as well.Deformation, variably overprinting these sedimentary mélanges locally results in a secondary tectonic block-in-matrix textures in which there may be “blocks” formed of matrix surrounded by more strongly deformed matrix.
Based on the following published papers:
Wakabayashi, J., 2017, Structural context and variation ocean plate stratigraphy, Franciscan Complex of California: Insight into mélange origins and subduction-accretion processes: Progress in Earth and Planetary Sciences 4: 18, 23p., doi: 10.1186/s40645-017-0132-y
Wakabayashi, J., 2015, Anatomy of a subduction complex: Architecture of the Franciscan Complex, California, at multiple length and time scales: International Geology Review, v. 57, p. 669-746. doi:10.1080/00206814.2014.998728.
Wakabayashi, J. and Rowe, C., 2015, Whither the megathrust? Localization of large-scale subduction slip along a contact of a mélange. International Geology Review. v. 57, p. 854-870. doi:10.1080/00206814.2015.1020453
- Evolution of step-overs and bends along strike-slip faults: Implications for seismic hazards assessment.
Step-overs along strike-slip faults have been traditionally considered to grow in size and cumulative slip accommodation as more slip accrues on the parent strike-slip fault. In such a model with greater slip, a pull-apart basin grows larger and deeper and a restraining step-over generates more uplift and exhumation. Inspection of step-overs of the San Andreas fault system suggests that step-overs migrate with respect to material formerly within them. This requires progressive formation of new transfer structures in the direction of migration. This process appears to operate from the meters/tens of meters scale of sag ponds and small push-up blocks to multi-kilometer scale basins and uplifted welts, with the Mendocino Triple Junction region being perhaps the largest scale structure of this sort proposed. Migrating step-overs result in inversion at all scales from thrusted sag pond deposits to inverted large-scale sedimentary basins. This style of step-over migration complicates assessment of long-term displacement on strike-slip faults because the zone of displacement is commonly much broader than the active strand, and this also applies to more recent displacement and earthquake history. Accordingly, siting of paleoseismic trenches needs to address this potential complexity in order to most optimally capture the full fault slip rate (for fault-parallel trenches) and most complete earthquake histories (for fault-crossing trenches). In addition the migrating step-over mechanism leads to propagation of some fault stands and the dying out of activity on others. This may result in some faults with a large cumulative displacement that have little or no late Quaternary activity whereas some immature strands with little geomorphic expression may accommodate significant slip rate.
Based on the following published papers (but the paleoseismic implications are not in these papers):
Wakabayashi, J., 2007, Step-overs that migrate with respect to affected deposits: Field characteristics and speculation on some details of their evolution: in Cunningham, W.D., and Mann, P., eds. Tectonics of strike-slip releasing and restraining bends in continental and oceanic settings. Geological Society of London Special Publication 290, p. 169-188
Wakabayashi, J., Hengesh, J.V., and Sawyer, T.L.,2004, Four-dimensional transform fault processes: progressive evolution of step-overs and bends: Tectonophysics, v. 392, p. 279-301.
- Geomorphic evolution and Cenozoic tectonics of the Sierra Nevada, California, and alternative interpretations of paleoaltimetry data
Note: This work began with seismic hazard studies I did as a consultant in the northern Sierra Nevada in the early 1990s.
Although stable isotope paleoaltimetry data has been interpreted to show that late Cenozoic uplift of the Sierra Nevada did not take place, stratigraphic-geomorphic relationships indicate otherwise. Such relationships show negligible stream incision between Eocene and late Miocene/Pliocene time.Stream incision of up to ~1 km began at (from south to north) about 20 Ma in the Kern to Kings River drainages, between 6 and 10 Ma in the San Joaquin River drainage, 3.6 to 4 Ma in the Stanislaus and Mokelumne River drainages, and ca. 3 Ma in the American and Feather River drainages. These differences in incision timing greatly exceed the time of knickpoint retreat, based on the example of the North Fork Feather River, where the knickpoint may have retreated over 100 km in less than 300 ka based on ages of interfluve-capping andesites and an inset basalt flow. The knickpoint in the Stanislaus River may have retreated over 50 km in less than 400 ka based on somewhat looser constraints. Eocene paleochannels show lowest gradients parallel to the range axis, steepest ones perpendicular, and reaches with significant "uphill" gradients that rise in the paleo-downstream direction. Modern Sierran rivers lack this relationship. The azimuth-gradient relationships of paleochannels, especially the uphill gradients, require late Cenozoic tilting and uplift. Incision began in spite of decreasing discharge and increasing sediment load and must have resulted from steepening associated with tilting and uplift. Stable isotope paleoaltimetry apparently records a profile similar to the modern range and areas east of it, in spite of significant vertical deformation that postdates the age of the sampled deposits, suggesting fairly recent reequilibration, in contrast to the published interpretations of closed system behavior since the Oligocene or Eocene. Such apparent open system behavior agrees with studies showing progressive hydration of volcanic glass and the correspondence between weathering and erosion rates. Northward-younging initiation of late Cenozoic uplift and stream incision suggests a relationship with triple junction migration, possibly associated with slab window development, with a second uplift pulse related to delamination and limited to the southern Sierra (San Joaquin River drainage and southward). Basement features may have significantly influenced along and across-strike differences in Cenozoic tectonics and geomorphic response.
Based on the following published papers:
Wakabayashi, J., 2013, Paleochannels, stream incision, erosion, topographic evolution, and alternative explanations of paleoaltimetry, Sierra Nevada, California: Geosphere, v. 9, p. 192-215, doi:10.1130/GES00814.1
Wakabayashi, J., and Sawyer, T.L., 2001, Stream incision, tectonics, uplift, and evolution of topography of the Sierra Nevada, California: Journal of Geology, v. 109, p. 539-562.
Contact:
John Wakabayashi, Ph.D.
Professor of Geology
Department of Earth and Environmental Sciences
California State University, Fresno
jwakabayashi@csufresno.edu