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What's Shaking ISSUE 03 - February 2016 WHAT’S SHAKING newsletter of the THE NEVADA SEISMOLOGICAL LABORATORY Earthquake Update NEVADA Carson RENO City Maps of earthquakes located by the Nevada Seismo- logical Laboratory (NSL) between 1/1/16 and 1/31/16, within the NSL network (right). Truckee Meadows region (above), Hawthorne, Nevada area (bottom left) and the area surrounding Las Vegas, Nevada (bottom right). HAWTHORNE Earthquakes located by the NSL (1/1/16-1/31/16) ML Quantity 4.0+ 1 3.0-3.9 2 2.0-2.9 67 Nevada 1.0-1.9 478 National ML < 1.0 809 Security Site Total 1357 eismicity during January included a small sequence near Haw- Sthorne, Nevada (above), and a notable sequence near Enter- LAS VEGAS prise, Utah (right). The largest of these Hawthorne events measured M3.2, and several events greater than M2.0 were also recorded. An event (M4.3) that occurred near Enterprise, Utah shook several eastern Nevada communities on January 15, 2016. The Sheldon Sequence also continues to be active in northwestern Nevada. Maps compiled by D. Molisee (2016) www.graphicdiffer.comwww.seismo.unr.edu @NVSeismoLab1 DEVELOPMENTS NSL Graduate Students Leverage Funding from the National Science Foundation unding for Steve Angster and will focus on the Agai-Pai, Indian FIan Pierce has come from Head, Gumdrop, Benton Springs, a National Science Foundation and Petrified fault systems, while grant (Steve Wesnousky, lead PI) Ian will study the Tahoe, Carson, focused on the deformation pat- Antelope Valley, Smith Valley, Ma- tern and kinematics of the Walker son Valley, and Walker Lake fault Lane. The ultimate goal of this systems. All faults shown in the funded project is to develop a bet- map to the right. ter understanding for how geodeti- urrently, Steve has measured cally observed northwest directed and collected data used for right lateral transtensional shear is C dating samples on the most prom- accommodated within the earth’s inent faults, the Petrified Spring crust in the central Walker Lane. and Benton Springs fault, used to he Walker Lane is a region in determine Quaternary slip rates. Twestern Nevada that has a Ian is using high-resolution eleva- high strain rate, resulting in large tion datasets (which come from (M7) earthquakes. Using geodesy, airborne laser scanning data) to the amount of motion can be un- measure fault offsets, and cosmo- derstood in great detail. The role genic isotope dating to constrain of Steve and Ian in this project is the timing of these offsets. The to constrain the amount of right- combination of research by these lateral slip that has accrued dur- two researchers in the Nevada ing the Quaternary Period (the last Seismological Laboratory/Center 2.5 million years) on a set of right for Neotectonics will categorize lateral fault systems. Right lateral many of the dominant fault sys- faults result in side-to-side motion tems in the Walker Lane. rather than vertical motion. Steve ABOVE: The Walker Lane is a tectonic region of eastern California and Western Nevada. Faults in this system pose risks to all major urban populations in Nevada (both Las Vegas and Reno areas!). By studying these faults, researchers are able to better understand the risks these faults impose. LEFT: Ian Pierce (left) and Steve Angster (right) have worked to- gether on projects in the US and abroad in the Himalayan range after last year’s M7.8 earth- quake. This new funding from NSF allows them to use their skills to understand fault systems in western Nevada. 2 www.seismo.unr.edu RESEARCH & RESEARCHERS NSL Graduate Students and Post-doctoral Researcher conduct sediment core sampling offshore Southern California SL graduate students Rachel during this campaign, sample from noon to midnight and then midnight to NHatch and Courtney Brailo along sediment depths ranging from 10-40 noon). During watch, scientists col- with Post-doctoral researcher Dr. feet. These cores can be used to date lect the cores and also track pertinent Jayne Bormann recently collaborated offset sediment layers imaged in high data such as core sampling locations, with Scripps Institution of Oceanogra- resolution seismic data, analogous to lengths, and any collection issues. phy and the University of California, paleoseismic trenches seen on land. The cores are prepped for transport San Diego to collect oceanic sediment In addition, these cores also sample and onboard analysis. cores offshore Southern California. turbidite/debris layers that show the r. Jayne Bormann (below middle) The data collected using the Re- telltale signs of violent shaking due is more familiar with life on a search Vessel R/V Thomas Thomp- to past earthquakes, providing a time D research vessel, having participated son (pictured above) will be used to history for shaking in this region. in many previous seismic projects in constrain the timing of motion along or Rachel Hatch (below left), being 2013. Some of the cores collected will strike-slip faults offshore Southern aboard the R/V Thompson of- be used directly for Dr. Bormann’s re- California. F fered the opportunity to learn about search on the San Diego Trough fault hese cores sample sediments marine methods and ship operations and its history of large earthquakes Tcollected from the seafloor in cy- in a research environment. Shifts for along this heretofore poorly studied, lindrical sections. The cores collected the “science crew” last 12-hours (from major faultline offshore SoCal. NSL PhD Student Rachel Hatch works Dr. Jayne Boremann prepares a core Science crew works on deck to set up on deck of the R/V Thompson to docu- for transport and storage onshore for and retrieve cores. ment core details. analysis. www.seismo.unr.edu 3 http://pubs.usgs.gov/gip/2005/15/images/fig02.jpg HISTORICAL EVENT HIGHLIGHT 1700 Cascadia Earthquake https://upload.wikimedia.org/wikipedia/commons/7/72/Cascadia_earthquake_sources.png http://4.bp.blogspot.com/-oIRQfS-oVxI/Tv5oBMj-BrI/AAAAAAAABs8/Rf4nqFneh1I/s1600/gf.gif The Cascadia earthquake of 1700 occurred along the Cascadia subduction zone on January 26th. The size Did you know? of this event is estimated to have been between M8.7- M9.2. This event is often associated with the “Orphan Did you know that this event is Tsunami” in Japan because a destructive wave was well documented, but associated with a lack of accom- panying shaking. There was no earthquake in Japan that could have triggered such a tsunami! This suggests classified as a Megathrust that the tsunami originated elsewhere. Indicators for the earthquake offshore of Washington & Oregon come caused by the Juan de Fuca plate from native oral traditions originating from the Cascadia region. Anecdotal references to large shaking and subducting beneath the North flooding events have been noted; however no dates or times are definitive. In the 1990’s, scientists found American Plate. evidence of extreme ground shaking through debris layers found offshore of Washington and Oregon. Ad- Other examples of Megathrust ditionally, the strongest evidence discovered in the 1980’s is from forests killed by the exposure to salty ocean water as the coastline sank because of strain-release due to the megaquake. events in recent times include the 2004 “Boxing Day” Indian Ocean A recent article in the New Yorker brought attention to potential repeat events of comparable size. Read the earthquake & tsunami - respon- article at: http://www.newyorker.com/magazine/2015/07/20/the-really-big-one sible for killing 230,000 people. Recent fault studies at our lab focused near Tahoe and Truckee suggest portions of both the Mohawk Valley The 2011 Tōhoku earthquake and and Lake Tahoe faults may rupture in tandem with the Cascadia Subduction Zone -- highlighting that large tsunami was also a megathrust Cascadia events may cause triggering of other fault systems. Triggering of the our local faults represents an event. This event was responsible indirect but substantial seismic concern to the Reno/Tahoe region. for killing nearly 16,000 individu- als in Japan. 4 www.seismo.unr.edu.
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