DEVELOPING A DATABASE OF SEISMIC DATA OVER THE CASCADIA SUBDUCTION ZONE.

KHAWLH AL FARSI Author

04/02/2021 Added

17 Plays

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the project focuses on developing a database of publicly available seismic surveys, over the subducting Juan de Fuca plate. The database will be used to investigate the major subsurface geological structures of the Cascadia subduction zone.

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[00:00:00.000]Hello, everyone.
[00:00:02.170]This is Khawlh Al Farsi.
[00:00:03.940]I am an undergraduate senior geology student.
[00:00:07.570]I'll be presenting today
[00:00:09.430]about
[00:00:10.263]a part of my graduation thesis,
[00:00:12.380]which is on geophysical research.
[00:00:15.120]This presentation is gonna be about,
[00:00:17.020]'Developing a Database of Seismic Data
[00:00:19.510]Over the Cascadia Subduction Zone'.
[00:00:22.010]So let's get started.
[00:00:24.390]In this presentation I'll discuss
[00:00:26.350]geological background of the area of interest,
[00:00:30.000]purpose of this project, methods, results,
[00:00:33.670]future directions of the research.
[00:00:35.560]And finally,
[00:00:36.620]some acknowledgements.
[00:00:39.870]This Project covers the region where
[00:00:41.960]the oceanic Juan de Fuca tectonic plate subduction
[00:00:45.410]is taking place
[00:00:46.880]underneath the West coast of the continent of North America
[00:00:51.780]which is known as the Cascadia Subduction Zone.
[00:00:54.590]As it's shown in the cross section below.
[00:00:58.470]Subduction zones generally process
[00:01:00.720]as two tectonic plates,
[00:01:02.600]move past each other
[00:01:04.870]and collide.
[00:01:06.230]Subduction zones represent some
[00:01:08.780]of the most devastating earthquakes on earth.
[00:01:12.690]This region is a part of the earth's famous ring of fire
[00:01:16.910]and it's seismically active,
[00:01:19.060]where deep earthquakes and volcanoes are expected.
[00:01:24.320]According to the US geological survey,
[00:01:27.140]there are evidence of megathrust earthquakes,
[00:01:30.360]of a magnitude of more than eight
[00:01:33.800]in the geological past of this region.
[00:01:37.340]As it's shown in the map on the right,
[00:01:40.480]different circles show different magnitudes
[00:01:43.430]of earthquakes that were
[00:01:45.520]dedicated between
[00:01:47.210]1979
[00:01:49.160]to 2019.
[00:01:52.590]As we can notice from the map,
[00:01:54.630]there is a gap on earthquakes
[00:01:56.640]right where the Cascadia Subduction Zone is located.
[00:02:00.840]We can define earthquakes generally as being
[00:02:04.917]"The sudden release of stored energy in earth's crust
[00:02:09.780]due to different stresses."
[00:02:12.050]The gap on releasing this energy,
[00:02:15.360]and the gap on earthquakes in this region means that
[00:02:19.940]this energy is not being released
[00:02:22.230]and it's been stored in the sub surface,
[00:02:26.010]which can lead us to the
[00:02:29.260]expectation of
[00:02:30.670]having
[00:02:32.361]another
[00:02:33.910]devastating megathrust earthquakes
[00:02:37.320]in this area soon.
[00:02:40.000]It's important to understand the geology
[00:02:42.400]of this active tectonic boundary
[00:02:44.460]in order to comprehend the overall subduction process
[00:02:48.000]and associated seismic hazards.
[00:02:52.980]This project focuses on developing a geophysical database
[00:02:57.210]of publicly available seismic reflection surveys
[00:03:00.940]over the Cascadia Subduction Zone.
[00:03:03.950]As the map on the right show,
[00:03:06.080]the study area of interest which is the,
[00:03:09.100]Juan de Fuca Plate,
[00:03:10.580]consists of different tectonic structures,
[00:03:13.610]such as spreading centers,
[00:03:16.030]active transform faults,
[00:03:18.510]Pseudo faults,
[00:03:19.343]and seamounts.
[00:03:21.150]These tectonic structures are seen in eight
[00:03:25.180]publicly available seismic reflection surveys,
[00:03:29.080]that were acquired between 1964 and 2017.
[00:03:38.250]The methodology was to develop this geophysical database,
[00:03:42.510]focuses on using publicly available reflection images
[00:03:47.060]and seismic data.
[00:03:48.870]The objective here is to
[00:03:50.730]stitch
[00:03:51.780]individual
[00:03:52.860]images
[00:03:54.660]into a coherent profile.
[00:03:57.260]As it's shown here,
[00:03:59.920]these are seismic images as found
[00:04:02.350]in the publicly available reflection data,
[00:04:06.310]RC1501 Survey as an example.
[00:04:09.210]This is a portion
[00:04:10.440]of RRC1501 Survey between three
[00:04:14.990]to seven.
[00:04:16.680]As we can see,
[00:04:17.710]images are found old
[00:04:21.050]in different sizes and shapes.
[00:04:24.800]We can notice the differences
[00:04:26.938]after stitching these images together,
[00:04:30.190]how the features now,
[00:04:32.330]the sedimentary features are.
[00:04:35.770]The structural features are aligned together.
[00:04:38.400]And how, for example,
[00:04:41.140]image seven and image three
[00:04:43.410]are cropped and flipped.
[00:04:46.893]And now we can identify different structural features
[00:04:50.780]to make more sense geologically.
[00:04:54.540]This stitching method requires a lot of understanding
[00:04:58.350]of the ongoing geological process,
[00:05:00.820]and it's challenged over
[00:05:03.230]the horizontal and vertical scaling,
[00:05:06.430]that is guided by,
[00:05:08.800]founded and computed bathymetry data.
[00:05:14.250]So, the objective of developing a full geological profile
[00:05:18.740]with tectonic architectures
[00:05:21.200]using seismic data is achieved for the region,
[00:05:26.060]using different parts of reflection surveys
[00:05:29.270]just as it's shown in this slide.
[00:05:31.800]This is another portion of the survey, RC1501.
[00:05:35.730]Now we are between two to three.
[00:05:40.585]We can see in this portion,
[00:05:42.360]there are
[00:05:43.440]different structural
[00:05:45.290]and architectural features
[00:05:48.040]that we can notice,
[00:05:50.550]that are different from the previous slide.
[00:05:54.030]The point here is
[00:05:55.270]that we can notice how structural features varies
[00:05:58.610]along one single survey.
[00:06:01.400]As we move to different locations
[00:06:03.560]along the seismic line of that survey.
[00:06:06.090]And as direction changes.
[00:06:13.850]The composed database will be used for future 2D Modeling
[00:06:17.320]of major sub-surface geological structures,
[00:06:21.290]over the Cascadia Subduction Zone.
[00:06:24.630]A future direction is also to develop
[00:06:30.720]maps,
[00:06:31.553]and to integrate seismic database
[00:06:33.620]with other geophysical data sets,
[00:06:36.110]namely gravity and magnetic fields
[00:06:38.690]as shown in grid maps below.
[00:06:41.830]Structural features and cross cell architectures
[00:06:44.750]of this active tectonic margin.
[00:06:47.520]The Cascadia Subduction Zone
[00:06:49.500]are important to understand the ongoing geology
[00:06:53.200]and to prepare for an eminent megathrust earthquake
[00:06:57.310]at this margin.
[00:06:58.810]That will affect greatly the population
[00:07:01.480]of the North Western US and Canada.
[00:07:06.490]Finally,
[00:07:07.323]I would like to make some acknowledgments.
[00:07:10.060]First, to the leader of the UNL geophysics research team,
[00:07:14.870]Dr. Irina Filina,
[00:07:16.520]for allowing me to be a part of this research project.
[00:07:21.850]Also to my geophysics teammate, Asif Ashraf,
[00:07:25.270]for his support,
[00:07:27.900]and to the Department of Earth and Atmospheric Sciences
[00:07:31.250]at
[00:07:32.083]College of Arts and Sciences
[00:07:35.170]of the University of Nebraska-Lincoln,
[00:07:38.060]for making this opportunity possible.
[00:07:41.070]I would also like to thank the Undergraduate Student
[00:07:44.570]Research and Creative Activities Exhibition,
[00:07:47.880]for providing me the chance to showcase my research project.
[00:07:53.120]Thank you for listening.

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DEVELOPING A DATABASE OF SEISMIC DATA OVER THE CASCADIA SUBDUCTION ZONE.

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