[ghsc-seminars] FW: LHP Seminar, this Wed. (Oct. 14th): Dr. Sean Lahusen presenting "Deep-seated landslide susceptibility and triggering in the Oregon Coast Range"

Mon Oct 12 14:51:23 UTC 2020

Francis Kevin Rengers, Ph.D. | Geomorphologist
U.S. Geological Survey | Research Geologist
1711 Illinois St. Golden, CO 80401
office: 303-273-8637 | cell: 720-618-0351
https://www.usgs.gov/staff-profiles/francis-rengers

From: "Thomas, Matthew A" <matthewthomas at usgs.gov>
Date: Monday, October 12, 2020 at 7:54 AM
Subject: LHP Seminar, this Wed. (Oct. 14th): Dr. Sean Lahusen presenting "Deep-seated landslide susceptibility and triggering in the Oregon Coast Range"

Hi Folks,

The LHP Seminar will meet (virtually, via Microsoft Teams) this week on Wednesday, October 14th @ 1500 Mountain (MDT).

Dr. Sean Lahusen<https://www.linkedin.com/in/sean-lahusen-b251306b/> from the U.S. Geological Survey will be presenting, “Deep-seated landslide susceptibility and triggering in the Oregon Coast Range”:

The Tyee Formation of the central Oregon Coast Range (OCR) hosts thousands of deep-seated landslides that fundamentally shape the morphology of the landscape and pose a significant risk to the residents of coastal Oregon. Despite the proximity of the OCR to the Cascadia Subduction Zone megathrust, recent work suggests that rainfall, not large magnitude earthquakes, is the predominant trigger of bedrock landslides here. Previous research has shown landslide areal density increases to the north, where the ratio of siltstone to sandstone is highest. Our new manually mapped landslide inventory has revealed even more complexity: landslide density ranges from 0-13% of total area from west to east. To test whether lithology or structure can explain these patterns, we have started to analyze sedimentology, bedding attitudes, and estimated rock mass strength at dozens of sites across a 25x70 km east-west swath of the Tyee Mountain Member of the Tyee Formation. Preliminary findings suggest regions of high landslide density tend to be underlain by bedrock with a greater overall ratio of siltstone to sandstone, corroborating previous work in the region. Bedding thickness, which cannot be explained by siltstone ratio alone, also seems to be important. Regions with few to no deep-seated landslides are often underlain by the thickest sandstone beds, while regions with high landslide density tend to have thicker siltstone beds. Our study reveals higher variability in landslide density across the Tyee Mountain member than previously recognized that is likely due to changes in lithological properties within the same mapped geology. We argue that landslide susceptibility models could be improved by accounting for greater detail in lithologic properties within generalized geologic units.

Hope you can join us!

Seminar Connection Instructions:

-- Turn your VPN services off.

-- Join in via Microsoft Teams by clicking here<https://gcc02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fteams.microsoft.com%2Fdl%2Flauncher%2Flauncher.html%3Furl%3D%252f_%2523%252fl%252fmeetup-join%252f19%253ameeting_NmU4M2E3ZDktNmIwOS00Y2NkLWEyZmMtNGM3YTQwYjQxYTFm%2540thread.v2%252f0%253fcontext%253d%25257b%252522Tid%252522%25253a%2525220693b5ba-4b18-4d7b-9341-f32f400a5494%252522%25252c%252522Oid%252522%25253a%25252282b4c0ea-89e9-402c-8d2a-8f68ffac5319%252522%25257d%2526anon%253dtrue%26type%3Dmeetup-join%26deeplinkId%3D354c7d10-e11c-4bfa-9af2-9aee09c70a3f%26directDl%3Dtrue%26msLaunch%3Dtrue%26enableMobilePage%3Dfalse%26suppressPrompt%3Dtrue%23&data=02%7C01%7Cdon.lindsay%40conservation.ca.gov%7Ceb46b0e08e5a46e16e4008d8483d3f4f%7C4c5988ae5a0040e8b065a017f9c99494%7C0%7C0%7C637338775182060975&sdata=IkdKqk%2B850RhUB0mOBpac0TTS8zySWDpmlMGcE4kDpg%3D&reserved=0>.

Take care,

matt

Matthew A. Thomas
Research Hydrologist (Mendenhall Fellow)
1711 Illinois Street, Golden, CO 80401
office: 303-273-8588
cell: 720-417-9021

USGS<https://www.usgs.gov/staff-profiles/matthew-a-thomas> | ResearchGate<https://www.researchgate.net/profile/Matthew_Thomas27> | Google Scholar<https://scholar.google.com/citations?user=Hg7I2YcAAAAJ&hl=en>
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