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#geotechnical

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💧🌏 Greg Cocks

Linking Inca Terraces With Landslide Occurrence In The Ticsani Valley, Peru
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doi.org/10.3390/geosciences141 <-- shared paper
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[takes me back to my engineering geology days in the Southern Hemisphere, including my thesis – with a healthy dose of spatial analysis and modeling – and all with a specific use; what is not to like?]

photo - terraces in part of the Ticsani Valley, Peru
photos - (A) The main fluvial landforms in the AOI. The Carumas river can be seen here to be bounded by landslides affecting a fluvial terrace covered by agricultural terraces. (B) Landslides affecting a slope close to a community in the AOI. Note the construction of terraces on prior landslide deposits.
schematic / cross-section - Typical profile of terraces built in Southern Peru. Wall rocks are directly piled over an excavated trench in bedrock without mortar. An upward decreasing gradation is used to fill the internal portion of the wall in compacted layers. Fertile arable soil is placed in the top 30 cm.
imagery / map / schematic cross-section - (A) A 3D view of the San Cristobal landslide. (B) A 1:50,000 geological map of the landslide area, modified from [33]. Ki-mat = Matalaque Fm. P-Pi = Puno Fm. Q-pl = colluvial deposits, debris avalanche. Qp-vl-pi = pyroclastic deposits. Red line marks the topographic cross-section shown in A. (C) Cross-section of the San Cristobal landslide with estimated base groundwater conditions (blue) and materials boundaries (green) to be used for modeling and interpreted potential failure surfaces (dashed red).
Public *
💧🌏 Greg Cocks

Preliminary Observations of the 5 April 2024 Mw 4.8 New Jersey Earthquake
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doi.org/10.1785/0320240024 <-- shared paper
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doi.org/10.1785/0320240020 <-- shared paper
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doi.org/10.1177/87552930231215 <-- shared paper
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[This is ‘unusual’ seismic activity and shaking patterns for this part of the USA, on an ‘unmapped’ fault, and seemingly challenging existing models of earthquake risk in the region; while a 4.8 is not big, it must have been quite a surprise for the people in this heavily populated U.S. Northeast not used to such things (per the paper, the USGS estimated it was felt by some 42 million people.]

Map showing the chance of any level of damaging earthquake shaking in 100 years from the 2023 50-State National Seismic Hazard Model.
Photos of Taylor’s Mill taken before and after the 5 April 2024, earthquake.
(a) Topographic map showing a mainshock (yellow star) and seismicity (open circles) across geological units from west‐northwest to east‐southeast: Catskills, Highland, Newark basin, and Atlantic Coastal plain. Ramapo fault trending northeast runs through the epicentral area toward Peekskill, New York (NY) (red lines). Border faults between the geologic units–Highland and Newark basin continue southwest from the epicenter through Pennsylvania (PA). Three large known historical earthquakes, 30 November 1783 M 5.3 New Jersey, 1 September 1895 M 4.1 New Jersey, and 10 August 1884 M 5.5 New York, are plotted by red squares. The 2024 Tewksbury earthquake is ∼20 km west of the 1895 earthquake. (b) Contour map showing mainshock peak ground velocity (PGV) measured on transverse‐component records filtered at 0.3–10 Hz. Stations used for the PGV estimation and Lg relative source time function (RSTF) analysis are plotted as open and gray triangles, respectively.
Geologic map of the epicentral area simplified from Owens et al. (1998) and Drake et al. (1996) draped over topography showing mapped faults (black lines), initial aftershock locations from U.S. Geological Survey (USGS) Comprehensive Earthquake Catalog (ComCat; U.S. Geological Survey [USGS], 2017; downloaded 7 April 2024, at 13:59 UTC; purple circles), and mainshock focal mechanism (see Data and Resources). The location of seismic station BRNJ, which was not recording during the mainshock, is shown by the red square. The New Jersey Highlands, composed of Mesoproterozoic to Ordovician igneous and metamorphic rocks, are shown to the northwest of the white line, and the Newark basin, composed of Mesozoic sedimentary and volcanic rocks, lies to the southeast. Background image is a shaded relief derived from the 10 m National Elevation Dataset (see Data and Resources). Seismicity in inset (gray dots and yellow stars) is from the USGS ComCat (USGS, 2017). The blue rectangle in the inset map indicates the region depicted in the larger figure.
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