TY  - JOUR
A1  - Kübler, Simon
A1  - Streich, R.
A1  - Lück, Erika
A1  - Hoffmann, M.
A1  - Friedrich, A. M.
A1  - Strecker, Manfred
T1  - Active faulting in a populated low-strain setting (Lower Rhine Graben, Central Europe) identified by geomorphic, geophysical and geological analysis
JF  - Seismicity, fault rupture and earthquake hazards in slowly deforming regions
N2  - The Lower Rhine Graben (Central Europe) is a prime example of a seismically active low-strain rift zone characterized by pronounced anthropogenic and climatic overprint of structures, and long recurrence intervals of large earthquakes. These factors render the identification of active faults and surface ruptures difficult. We investigated two fault scarps in the Lower Rhine Graben, to decipher their structural character, offset and potential seismogenic origin. Both scarps were modified by anthropogenic activity. The Hemmerich site lies c. 20 km SW of Cologne, along the Erft Fault. The Untermaubach site lies SW of Duren, where the Schafberg Fault projects into the Rur River valley. At the Hemmerich site, geomorphic and geophysical data, as well as exploratory coring reveal evidence of repeated normal faulting. Geophysical analysis and palaeoseismological excavation at the Untermaubach site reveal a complex fault zone in Holocene gravels characterized by subtle gravel deformation. Differentiation of tectonic and fluvial features was only possible with trenching, because fault structures and grain sizes of the sediments were below the resolution of the geophysical data. Despite these issues, our investigation demonstrates that valuable insight into past earthquakes and seismogenic deformation in a low-strain environment can be revealed using a multidisciplinary approach.
Y1  - 2017
SN  - 978-1-86239-745-3
SN  - 978-1-86239-964-8
U6  - https://doi.org/10.1144/SP432.11
SN  - 0305-8719
VL  - 432
SP  - 127
EP  - 146
PB  - The Geological Society
CY  - London
ER  - 
TY  - JOUR
A1  - Bennett, Richard A.
A1  - Friedrich, A. M.
A1  - Furlong, K. P.
T1  - Codependent histories of the San Andreas and San Jacinto fault zones from inversion of fault displacement rates
N2  - The displacement histories of the San Jacinto and southernmost San Andreas fault zones are constrained by offset data with ages in the range of 5 Ma to 5 ka. Apparent discrepancies between long- and short-term average displacement rates can be reconciled with a time-variable rate model. In this model, the displacement rate on the San Andreas decelerated from similar to35 mm/yr at 1.5 Ma to as low as 9 +/- 4 mm/yr by 90 ka. Over this same time period, the rate on the San Jacinto fault zone accelerated from an initial value of zero to a rate of 26 +/- 4 mm/yr. The data also imply that the rate of the San Andreas fault accelerated since ca. 90 ka, from similar to9 mm/yr to the modern rate of 27 +/- 4 mm/yr, whereas the San Jacinto decelerated from 26 +/- 4 mm/yr to the modern rate of 8 +/- 4 mm/yr. The time scale of these changes is significantly longer than the earthquake cycle, but shorter than time scales characteristic of lithospheric-scalle dynamics. The emergence of the San Jacinto fault zone ca. 1.5 Ma coincided with the development of a major restraining bend in the San Andreas fault zone, suggesting that the formation of new subparallell faults could be driven by conditions that inhibit displacement on preexisting faults
Y1  - 2004
SN  - 0091-7613
ER  - 
TY  - JOUR
A1  - Stein, S.
A1  - Friedrich, A. M.
A1  - Newman, A.
T1  - Dependence of possible characteristic earthquakes on spatial sampling: Illustration for the Wasatch seismic zone, Utah
Y1  - 2005
SN  - 0895-0695
ER  - 
TY  - JOUR
A1  - Friedrich, A. M.
A1  - Lee, J.
A1  - Wernicke, B. P.
A1  - Sieh, K.
T1  - Geologic context of geodetic data across a Basin and Range normal fault, Crescent Valley, Nevada
N2  - [1] Geodetic strain and late Quaternary faulting in the Basin and Range province is distributed over a region much wider than historic seismicity, which is localized near the margins of the province. In the relatively aseismic interior, both the magnitude and direction of geodetic strain may be inconsistent with the Holocene faulting record. We document the best example of such a disagreement across the NE striking, similar to55degrees NW dipping Crescent normal fault, where a NW oriented, 70 km geodetic baseline records contemporary shortening of similar to2 mm/yr orthogonal to the fault trace. In contrast, our geomorphic, paleoseismic, and geochronologic analyses of the Crescent fault suggest that a large extensional rupture occurred during the late Holocene epoch. An excavation across the fault at Fourmile Canyon reveals that the most recent event occurred at 2.8 +/- 0.1 ka, with net vertical tectonic displacement of 4.6 +/- 0.4 m at this location, corresponding to the release of similar to3 m of accumulated NW-SE extension. Measured alluvial scarp profiles suggest a minimum rupture length of 30 km along the range front for the event, implying a moment magnitude M-w of at least 6.6. No prior event occurred between similar to2.8 ka and similar to6.4 +/- 0.1 ka, the C-14 calender age of strata near the base of the exposed section. Assuming typical slip rates for Basin and Range faults (similar to0.3 mm/yr), these results imply that up to one third, or similar to1 m, of the extensional strain released in the previous earthquake could have reaccumulated across the fault since similar to2.8 ka. However, the contemporary shortening implies that the fault is unloading due to a transient process, whose duration is limited to between 6 years ( geodetic recording time) and 2.8 ka ( the age of the most recent event). These results emphasize the importance of providing accurate geologic data on the timescale of the earthquake cycle in order to evaluate geodetic measurements
Y1  - 2004
SN  - 0278-7407
ER  -