abstract
Article history:
Received 25 February 2015
Received in revised form 18 November 2015
Accepted 28 November 2015
Available online 1 December 2015
Earthquake and tsunami records on centennial and millennial temporal scales are necessary to understanding
long-term subduction zone behavior and the occurrences of large, but infrequent events. Microfossils, such as
diatoms, incorporated into coastal stratigraphy provide some of the most detailed reconstructions of the history
of earthquakes and tsunamis. We explore qualitative and quantitative techniques that employ the relation between
diatoms and salinity, tidal elevation, and life form to: (1) reconstruct records of vertical land-level change
associated with large earthquakes; and (2) identify anomalous sand and silt beds deposited by tsunamis. A global
database shows that diatoms have been successfully employed in the reconstruction of earthquake and tsunami
histories in Chile, the Indian Ocean, Japan, New Zealand, the North Sea, the Pacific Northwest of North America,
and the South Pacific. We use case studies from some of these locations to highlight advancements in the field
and new capabilities that diatoms have enabled. Examples from the Pacific Northwest of North America illustrate
the evolution of quantitative diatom-based reconstructions of earthquake-related land-level change. In Alaska
and Japan, diatoms have documented land-level changes throughout the earthquake deformation cycle, including
possible preseismic land-level change signals and postseismic deformation. Diatoms helped identify
coseismic uplift along the central Chile subduction zone coast, and uplift and subsidence along the Alaska–
Aleutian megathrust, expanding our knowledge of the variability of slip in megathrust ruptures. In tsunami
studies, diatoms help determine the provenance of anomalous sands and silts found in low-energy coastal stratigraphic
sequences. In Japan, allochthonous marine and brackish diatoms within sand deposits signaled repeated
marine incursions into a coastal lake, helping identify a possible predecessor to the 2011 Tohoku tsunami. In
the Pacific Northwest of North America and Chile, diatoms were used to estimate tsunami run-up beyond the
landward limit of tsunami sedimentation. Examples from the North Sea, Thailand, and Japan show how the fragmentation
and sorting of diatom valves may provide evidence of high-energy transport during the rapid, turbulent
flow of a tsunami. To conclude, we emphasize the importance of studying the modern diatom response to
changes in land level and/or tsunami inundation to improve diatom-based records of prehistoric earthquakes
and tsunamis.
abstractArticle history:Received 25 February 2015Received in revised form 18 November 2015Accepted 28 November 2015Available online 1 December 2015Earthquake and tsunami records on centennial and millennial temporal scales are necessary to understandinglong-term subduction zone behavior and the occurrences of large, but infrequent events. Microfossils, such asdiatoms, incorporated into coastal stratigraphy provide some of the most detailed reconstructions of the historyof earthquakes and tsunamis. We explore qualitative and quantitative techniques that employ the relation betweendiatoms and salinity, tidal elevation, and life form to: (1) reconstruct records of vertical land-level changeassociated with large earthquakes; and (2) identify anomalous sand and silt beds deposited by tsunamis. A globaldatabase shows that diatoms have been successfully employed in the reconstruction of earthquake and tsunamihistories in Chile, the Indian Ocean, Japan, New Zealand, the North Sea, the Pacific Northwest of North America,and the South Pacific. We use case studies from some of these locations to highlight advancements in the fieldand new capabilities that diatoms have enabled. Examples from the Pacific Northwest of North America illustratethe evolution of quantitative diatom-based reconstructions of earthquake-related land-level change. In Alaskaand Japan, diatoms have documented land-level changes throughout the earthquake deformation cycle, includingpossible preseismic land-level change signals and postseismic deformation. Diatoms helped identifycoseismic uplift along the central Chile subduction zone coast, and uplift and subsidence along the Alaska–Aleutian megathrust, expanding our knowledge of the variability of slip in megathrust ruptures. In tsunamistudies, diatoms help determine the provenance of anomalous sands and silts found in low-energy coastal stratigraphicsequences. In Japan, allochthonous marine and brackish diatoms within sand deposits signaled repeatedmarine incursions into a coastal lake, helping identify a possible predecessor to the 2011 Tohoku tsunami. Inthe Pacific Northwest of North America and Chile, diatoms were used to estimate tsunami run-up beyond thelandward limit of tsunami sedimentation. Examples from the North Sea, Thailand, and Japan show how the fragmentationand sorting of diatom valves may provide evidence of high-energy transport during the rapid, turbulentflow of a tsunami. To conclude, we emphasize the importance of studying the modern diatom response tochanges in land level and/or tsunami inundation to improve diatom-based records of prehistoric earthquakesand tsunamis.
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