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Articles 1 - 6 of 6
Full-Text Articles in Physical Sciences and Mathematics
Age Estimates And Uplift Rates For Late Pleistocene Marine Terraces' Southern Oregon Portion Of The Cascadia Forearc, Daniel R. Muhs, Harvey M. Kelsey, Gifford H. Miller, Geoge L. Kennedy, Joseph F. Whelan, Galan W. Mcinelly
Age Estimates And Uplift Rates For Late Pleistocene Marine Terraces' Southern Oregon Portion Of The Cascadia Forearc, Daniel R. Muhs, Harvey M. Kelsey, Gifford H. Miller, Geoge L. Kennedy, Joseph F. Whelan, Galan W. Mcinelly
United States Geological Survey: Staff Publications
Marine terraces are prominent landforms along the southern Oregon coast, which forms part of the forearc region of the Cascadia subduction zone. Interest in the Cascadia subduction zone has increased because recent investigations have suggested that slip along plates at certain types of convergent margins is characteristically accompanied by large earthquakes. In addition, other investigations have suggested that convergent margins can be broadly classified by the magnitude of their uplift rates. With these hypotheses in mind, we generated new uranium series, amino acid, and stable isotope data for southern Oregon marine terrace fossils. These data, along with terrace elevations and …
Sedimentary Paleoenvironments Of Fossil Platyrrhine Localities, Miocene Pinturas Formation, Santa Cruz Province, Argentina, Thomas Bown, Claudio N. Larriestra
Sedimentary Paleoenvironments Of Fossil Platyrrhine Localities, Miocene Pinturas Formation, Santa Cruz Province, Argentina, Thomas Bown, Claudio N. Larriestra
United States Geological Survey: Staff Publications
The Pinturas Formation is a pyroclastic and epiclastic aeolian deposit of Miocene age lying discordantly upon Jurassic rocks in the elevated Andean precordillera of northwest Santa Cruz Province, Argentina. The history of de\'elopment of the Pinturas Formation was significantly affected by the gradual, though sporadic, draping of this aeolian sediment across a profound, slowly filling paleotopography. The Pinturas depositional cycle consisted of: (1) minor aeolian deposition followed by soil formation, and (2) major aeolian deposition followed by intervals of regional erosion. Fluvial action seems to have been almost wholly confined to intraformational erosion, and two significant intraformational erosional unconformities divide …
Crustal Strain Near The Big Bend Of The San Andreas Fault: Analysis Of The Los Padres-Tehachapi Trilateration Networks, California, Donna Eberhart-Phillips, Michael Lisowski, Mark D. Zoback
Crustal Strain Near The Big Bend Of The San Andreas Fault: Analysis Of The Los Padres-Tehachapi Trilateration Networks, California, Donna Eberhart-Phillips, Michael Lisowski, Mark D. Zoback
United States Geological Survey: Staff Publications
In the region of the Los Padres-Tehachapi geodetic network, the San Andreas fault (SAF) changes its orientation by over 30 ° from N40 °W, close to that predicted by plate motion for a transform boundary, to N73 °W. The strain orientation near the SAF is consistent with right-lateral shear along the fault, with maximum shear rate of 0.38 ± 0.01 μrad/yr at N63 °W. In contrast, away from the SAF the strain orientations on both sides of the fault are consistent with the plate motion direction, with maximum shear rate of 0.19 ± 0.01 μrad/yr at N44 °W. The strain …
Coseismic Stress Changes Induced By The 1989 Loma Prieta, California Earthquake, Andrew J. Michael, William L. Ellsworth, David H. Oppenheimer
Coseismic Stress Changes Induced By The 1989 Loma Prieta, California Earthquake, Andrew J. Michael, William L. Ellsworth, David H. Oppenheimer
United States Geological Survey: Staff Publications
Earthquake focal mechanisms from before and after the 1989 Loma Prieta, California earthquake are used to infer the coseismic stress change. Before the main shock, most earthquakes correspond to right lateral slip on planes sub-parallel to the San Andreas fault, and imply a generally N-S most compressionsal stress axis anda vertical intermediate stress axis. Aftershocks within the main shock rupture zone, however, display almost every style and orientation of faulting, implying an extremely heterogeneous stress field. This suggests that the main shock relieved most, if not all, of the shear stress acting on its fault plane. Aftershocks that lie on …
The October 17, 1989, Loma Prieta, California, Earthquake And Its Aftershocks: Geometry Of The Sequence From High-Resolution Locations, Lynn D. Dietz, William L. Ellsworth
The October 17, 1989, Loma Prieta, California, Earthquake And Its Aftershocks: Geometry Of The Sequence From High-Resolution Locations, Lynn D. Dietz, William L. Ellsworth
United States Geological Survey: Staff Publications
Hypocenters of the Loma Prieta sequence form a dipping zone that rises from the mainshock hypocenter and is parallel to the mainshock nodal plane. Most aftershocks cluster around the perimeter of the zone, surrounding a relatively aseismic center which approximates the region of mainshock rapture. At its southeastern end, the dipping aftershock zone warps into a vertical surface that corresponds to the San Andreas fault. In the central and northwestern parts of the zone at depths above -10 km, the aftershocks define numerous disjoint fault structures. The large component of reverse-slip observed in this event agrees with a simple model …
Phytoplankton Dynamics In Three Rocky Mountain Lakes, Colorado, U.S.A., Diane M. Mcknight, Richard L. Smith, J. Platt Bradbury, Jill S. Baron, Sarah Spaulding
Phytoplankton Dynamics In Three Rocky Mountain Lakes, Colorado, U.S.A., Diane M. Mcknight, Richard L. Smith, J. Platt Bradbury, Jill S. Baron, Sarah Spaulding
United States Geological Survey: Staff Publications
In 1984 and 1985 seasonal changes in phytoplankton were studied in a system of three lakes in Loch Vale, Rocky Mountain National Park, Colorado. Three periods were evident: (1) A spring bloom, during snowmelt, of the planktonic diatom Asterionella Formosa, (2) a mid- summer period of minimal algal abundance, and (3) a fall bloom of the blue-green alga Oscillatoria limnetica. Seasonal phytoplankton dynamics in these lakes are controlled partially by the rapid flushing rate during snowmelt and the transport of phytoplankton from the highest lake to the lower lakes by the stream, Icy Brook. During snowmelt, the A. …