Category Archives: oceanography

Mw 7.8 Earthquake in the Scotia Sea

We just got another large earthquake in this region, of magnitude 7.8. There were some changes in magnitudes and epicentral locations early on. It is still early and may change more. Earlier there was a M6.8 earthquake nearby, along with a couple ~M5. These earthquakes are probably occurring on a transform fault system that is connected on the east to the oceanic Scotia subduction zone.

This USGS fault data set is at a global scale and so may not account for the latest structural relations on a local scale. The magnetic anomaly data for the plates in this region are pretty well mapped in some places, but the complexities arise near this earthquake series, south of the east-west transform fault. I have also plotted the historic seismicity with IRIS’ earthquake viewer. Their plate boundary faults are better located than the USGS fault locations, in places.

The moment tensor (an indicator of the type of earthquake and sense of motion during the earthquake) shows a similar sense of motion on this fault as the M6.8 recorded earlier. Based on the mapped plate boundary faults in this area, I interpret this to be a left-lateral strike-slip earthquake, with slightly oblique motion suggesting transtension. The bathymetry also may slightly support a n-s fault with right lateral motion. The transform fault here is stepping left, so left-lateral slip would generate transtension (extension). It is equivocal without a better fault map or high resolution bathymetry. There is a fault-parallel basin that may be related to a possible left step over. There are a couple lines of higher resolution bathymetry about 50-75 km due west of the epicenter that does show some ~”n20e” structures (see figure below). moment tensor

Here is the USGS page.

Here is a map of the area. The epicenter is marked by a red starmap region

Here is the same map with historic earthquakes plotted. map region

Here is the IRIS map with historic earthquakes plotted. IRIS puts together learning moment educational products for many larger earthquakes. Here is the IRIS earthquake browser. map region

Here is a map scaled to the USGS Modified Mercalli intensity map. map region

Here is the USGS pager page, which helps us to rapidly evaluate potential infrastructure damages. map region

Here is a tide gage record from Paul Whitmore at the NOAA/NWS National Tsunami Warning Center. The tide gage is located on South Georgia Island. map region

Here is a figure from Lindeque et al., 2013 showing one tectonic model of this region (Marine Geology, V. 336, p 61-63). Their paper investigates the Cretaceous to Quaternary sedimentation history of the Weddel and Scotia seas. They use seismic stratigraphic profiles and sediment cores to evaluate the sources and timing of sedimentation. They interpret these sediments in terms of oceanographic circulation patterns that changed following the tectonic evolution of this margin. In the Cretaceous, the deep water gateway was closed and the subduction zone along southern Chile probably connected with the subduction zone off the Antarctic Peninsula. Here is a link to their paper. map region

Here is a map of the region from wiki commons http://commons.wikimedia.org/wiki/File:Scotia-sea.png. map region

Here is a map of the local area showing evidence for both e-w faulting (A) and ne-sw faulting (B). map region

Here is a video map showing seismic waves from this earthquake radiate through the seismic network in the US. (9.6 MB mp4) map region

Here is a great paper on the tectonic evolution of the western Scotia Sea.

Here is a great web page with tectonic reconstructions of this region.

Here is one of their maps:

M 7.3 offshore Honshu Japan

Extensional earthquake in Pacific plate “up-dip” of the 11 March 2011 Tohoku-Oki earthquake.

Here is the USGS page.

Here is the moment tensor:
M7.3 Honshu

Here is a map of the epicenter and Japan:
M7.3 Honshu

Here is a map of the epicenter and Japan with historic seismicity (dominated by 2011):
M7.3 Honshu

Here is a zoomed in map of the epicenter and Japan with the “did you feel it” overlay on land:
M7.3 Honshu

Here is a zoomed in map of the epicenter and Japan with the Intensity Contours plotted:
M7.3 Honshu

Here is the usgs map for the region:
M7.3 Honshu

Here is the moment tensor page:
M7.3 Honshu

Here is the PAGER page:
M7.3 Honshu

Hookton Slough Coring

Tom Leroy and I went to my old coring site 01-BR-05 to make sure it was usable as a field trip stop for my class. We will be going here this coming Wednesday. Thanks Tom for helping me out.

I will write more about these cores and what our interpretations are after the field trip. I want the class to come up with their own interpretations. I have a few photos of the core we collected today.

This is an overall view of the 3rd core section down. This core samples sediment of approximately 1 meter in length. This core sampled sediment from approximately 1.8 to 2.8 meters. Up is to the left. The base of the core includes blue-gray silty-clay, overlain by an organic rich brown muddy peat, overlain by a clean mud and then a series of muddy sand and sandy mud layers, which is finally overlain by some more mud. Some of the mud has darker grey layers.

Here is an overall view of the middle of the core.01-BR-05

Here is a “zoom in” of the middle of the core.01-BR-05

Here is a map of the regional tectonics.01-BR-05

IPCC 5th Assessment Report Forthcoming

Coming out later this month here http://www.climatechange2013.org/report/

i pasted some text from the group I fact sheet that demonstrates why the IPCC assessment reports are the most comprehensive and peer reviewed science ever. 9,200 references! ~55,000 comments! no single paper published anywhere at any time has been so comprehensive. single papers, which may disagree with minor aspects of the ARs, pale in comparison (but continue to be used by blog writers to attempt to discredit the AR). single authors also attempt to raise questions, but frequently they are only experts in a minor or related field (eg Don Easterbrook, world class glaciologist, but not a climatologist).

you have questions? WG1AR5_Questions.pdf

you want to read the fact sheet? WG1AR5_Questions.pdf

The Report
1 Scoping Meeting to outline 14 Chapters Over 1000 nominations from 63 countries
209 Lead Authors and 50 Review Editors from 39 countries Over 600 Contributing Authors from 32 countries Over 2 million gigabytes of numerical data from climate model simulations Over 9200 scientific publications cited

The First Order Draft Expert Review
Nearly 1500 individuals registered 21,400 comments from 659 Expert Reviewers from
47 countries

The Second Order Draft Expert and Government Review
Over 1500 individuals registered 31,422 comments from 800 Expert Reviewers from
46 countries and 26 Governments

The Final Government Distribution
1855 comments from 32 Governments on the Final Draft Summary for Policymakers

Total Reviews
54,677 comments 1089 Expert Reviewers from 55 countries 38 Governments

Fall 2013 Geosciences Courses – College of the Redwoods, Eureka

There are several Earth Science courses taught at College of the Redwoods this coming Fall Semester. These are listed below. Please visit http://www.redwoods.edu/admissions/guide/ to register for any of these classes.

Environmental Science 15 Introduction to Energy 3 units An introductory study of humanity’s past and present use of available energy resources and an examination of potential future directions in energy use. Students will learn about the physical principles of energy resources and consider issues of environmental impact, economics, and sustainability.

Geology 1 Physical Geology 4 units An introductory study of physical geology including earth processes, materials, and changes in these materials through geologic time. Students will study minerals and rocks in the lab and the field, and will explore principles of mineral and rock formation, landform development, plate tectonics, volcanism, folding and faulting, and related topics.

Geology 15 Introduction to Earthquakes and Geologic Hazards 3 units An investigation of geologic and plate-tectonic processes and their relationships to faults, earthquake activity, mountain building, volcanism, landform development, and natural disasters. The course explores plate interactions and the connection to historic geologic disasters including earthquakes, tsunami, and volcanic eruptions. Students will learn about hazard prediction, preparedness, and societal responses to living within a dynamic geologic environment. Here is the website for this course.

Oceanography 10 Introduction to Oceanography 3 units An introduction to the Earth’s ocean including marine environments, geology, plate tectonics, fundamental chemical and physical properties of seawater, atmospheric-oceanic relationships, oceanic circulation, coastal environments and biological productivity. (linked to Oceanography 11)

Oceanography 11 Lab in Oceanography 1 units An exploration of the conceptual material presented in OCEAN-10. Students will acquire practical laboratory and field experience using oceanographic skills, tests, and procedures. Laboratory exercises focus on chart reading, measurements of seafloor movement, seawater chemistry, wave celerity, and microscopic analysis. Field experience includes examination of coastal geology, wave and beach processes, habitats and marine organisms. (linked to Oceanography 10)