@article{BrickerSchwanghartAdhikarietal.2017, author = {Bricker, Jeremy D. and Schwanghart, Wolfgang and Adhikari, Basanta Raj and Moriguchi, Shuji and Roeber, Volker and Giri, Sanjay}, title = {Performance of Models for Flash Flood Warning and Hazard Assessment}, series = {Mountain research and development}, volume = {37}, journal = {Mountain research and development}, number = {1}, publisher = {International Mountain Society}, address = {Lawrence}, issn = {0276-4741}, doi = {10.1659/MRD-JOURNAL-D-16-00043.1}, pages = {5 -- 15}, year = {2017}, abstract = {The 2015 magnitude 7.8 Gorkha earthquake and its aftershocks weakened mountain slopes in Nepal. Co- and postseismic landsliding and the formation of landslide-dammed lakes along steeply dissected valleys were widespread, among them a landslide that dammed the Kali Gandaki River. Overtopping of the landslide dam resulted in a flash flood downstream, though casualties were prevented because of timely evacuation of low-lying areas. We hindcast the flood using the BREACH physically based dam-break model for upstream hydrograph generation, and compared the resulting maximum flow rate with those resulting from various empirical formulas and a simplified hydrograph based on published observations. Subsequent modeling of downstream flood propagation was compromised by a coarse-resolution digital elevation model with several artifacts. Thus, we used a digital-elevation-model preprocessing technique that combined carving and smoothing to derive topographic data. We then applied the 1-dimensional HEC-RAS model for downstream flood routing, and compared it to the 2-dimensional Delft-FLOW model. Simulations were validated using rectified frames of a video recorded by a resident during the flood in the village of Beni, allowing estimation of maximum flow depth and speed. Results show that hydrological smoothing is necessary when using coarse topographic data (such as SRTM or ASTER), as using raw topography underestimates flow depth and speed and overestimates flood wave arrival lag time. Results also show that the 2-dimensional model produces more accurate results than the 1-dimensional model but the 1-dimensional model generates a more conservative result and can be run in a much shorter time. Therefore, a 2-dimensional model is recommended for hazard assessment and planning, whereas a 1-dimensional model would facilitate real-time warning declaration.}, language = {en} } @article{MelnickMorenoQuinterosetal.2017, author = {Melnick, Daniel and Moreno, Marcos and Quinteros, Javier and Carlos Baez, Juan and Deng, Zhiguo and Li, Shaoyang and Oncken, Onno}, title = {The super-interseismic phase of the megathrust earthquake cycle in Chile}, series = {Geophysical research letters}, volume = {44}, journal = {Geophysical research letters}, number = {2}, publisher = {American Geophysical Union}, address = {Washington}, issn = {0094-8276}, doi = {10.1002/2016GL071845}, pages = {784 -- 791}, year = {2017}, abstract = {Along a subduction zone, great megathrust earthquakes recur either after long seismic gaps lasting several decades to centuries or over much shorter periods lasting hours to a few years when cascading successions of earthquakes rupture nearby segments of the fault. We analyze a decade of continuous Global Positioning System observations along the South American continent to estimate changes in deformation rates between the 2010 Maule (M8.8) and 2015 Illapel (M8.3) Chilean earthquakes. We find that surface velocities increased after the 2010 earthquake, in response to continental-scale viscoelastic mantle relaxation and to regional-scale increased degree of interplate locking. We propose that increased locking occurs transiently during a super-interseismic phase in segments adjacent to a megathrust rupture, responding to bending of both plates caused by coseismic slip and subsequent afterslip. Enhanced strain rates during a super-interseismic phase may therefore bring a megathrust segment closer to failure and possibly triggered the 2015 event.}, language = {en} } @masterthesis{Lehmann2017, type = {Bachelor Thesis}, author = {Lehmann, Lukas}, title = {Performance Test von Phasenpickern}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-401993}, school = {Universit{\"a}t Potsdam}, pages = {I, 40, XXXIX}, year = {2017}, abstract = {Die genauen Einsatzzeiten seismischer P-Phasen von Erdbeben werden in SeisComP3 und anderen Auswerteprogrammen standardm{\"a}ßig und in Echtzeit automatisch bestimmt. S-Phasen stellen dagegen eine weit gr{\"o}ßere Herausforderung dar. Nur mit genauen Picks der P- bzw. S-Phasen k{\"o}nnen die Erdbebenlokationen korrekt und stabil bestimmt werden. Darum besteht erhebliches Interesse, diese mit hoher Genauigkeit zu bestimmen. Das Ziel der vorliegenden Bachelorarbeit war es, vier verschiedene, bereits vorhandene S-Phasenpicker auf ausgew{\"a}hlte Parameter optimal zu konfigurieren, auf Testdaten anzuwenden und deren Leistungsf{\"a}higkeit objektiv zu bewerten. Dazu wurden ein S-Picker (S-L2) aus dem OpenSource SeisComp3-Programmpaket, zwei S-Picker (S-AIC, S-AIC-V) als kommerzielles Modul der Firma gempa GmbH f{\"u}r SeisComP3 und ein S-Picker (Frequenzband) aus dem OpenSource PhasePaPy-Paket ausgew{\"a}hlt. Die Bewertung erfolgte durch Vergleich automatischer Picks mit manuell bestimmten Einsatzzeiten. Alle vier Picker wurden separat konfiguriert und auf drei verschiedene Datens{\"a}tze von Erdbeben in N-Chile und im Vogtland, Deutschland, angewandt. Dazu wurden regional bzw. lokal typische Erdbeben zuf{\"a}llig ausgew{\"a}hlt und die P- und S-Phasen manuell bestimmt. Mit den zu testenden S-Pickeralgorithmen wurden dieselben Daten durchsucht und die Picks automatisch bestimmt. Die Konfigurationen der Picker wurden gleichzeitig automatisch und objektiv durch iterative Anpassung optimiert. Ein neu erstelltes Bewertungssystem vergleicht die manuellen und die automatisch gefundenen S-Picks anhand von definierten Qualit{\"a}tsfaktoren. Die Qualit{\"a}tsfaktoren sind: der Mittelwert und die Standardabweichung der zeitlichen Differenzen zwischen den S-Picks, die Anzahl an {\"u}bereinstimmenden S-Picks, die Prozentangaben {\"u}ber m{\"o}gliche S-Picks und die ben{\"o}tigt Rechenzeit. Die objektive Bewertung erfolgte anhand eines Scores. Der Scorewert ergibt sich aus der gewichteten Summe folgender normierter Qualit{\"a}tsfaktoren: Standardabweichung (20\%), Mittelwert (20\%) und Prozentangabe {\"u}ber m{\"o}gliche S-Picks (60\%). Konfigurationen mit hohem Score werden bevorzugt. Die bevorzugten Konfigurationen der verschiedenen Picker wurden miteinander verglichen, um den am besten geeigneten S-Pickeralgorithmus zu bestimmen. Allgemein zeigt sich, dass der S-AIC Picker f{\"u}r jeden der drei Datens{\"a}tze die h{\"o}chsten Scores und damit die besten Ergebnisse liefert. Dabei wurde f{\"u}r jeden Datensatz ein andere Konfiguration der Parameter des S-AIC Pickers als die am besten geeignete bezeichnet. Daher ist f{\"u}r jede Erdbebenregion eine andere Konfigurationen erforderlich, um optimale Ergebnisse mit diesem S-Picker zu bekommen.}, language = {de} } @article{JaraMunozMelnickZambranoetal.2017, author = {Jara-Munoz, Julius and Melnick, Daniel and Zambrano, Patricio and Rietbrock, Andreas and Gonzalez, Javiera and Argandona, Boris and Strecker, Manfred}, title = {Quantifying offshore fore-arc deformation and splay-fault slip using drowned Pleistocene shorelines, Arauco Bay, Chile}, series = {Journal of geophysical research : Solid earth}, volume = {122}, journal = {Journal of geophysical research : Solid earth}, publisher = {American Geophysical Union}, address = {Washington}, issn = {2169-9313}, doi = {10.1002/2016JB013339}, pages = {4529 -- 4558}, year = {2017}, abstract = {Most of the deformation associated with the seismic cycle in subduction zones occurs offshore and has been therefore difficult to quantify with direct observations at millennial timescales. Here we study millennial deformation associated with an active splay-fault system in the Arauco Bay area off south central Chile. We describe hitherto unrecognized drowned shorelines using high-resolution multibeam bathymetry, geomorphic, sedimentologic, and paleontologic observations and quantify uplift rates using a Landscape Evolution Model. Along a margin-normal profile, uplift rates are 1.3m/ka near the edge of the continental shelf, 1.5m/ka at the emerged Santa Maria Island, -0.1m/ka at the center of the Arauco Bay, and 0.3m/ka in the mainland. The bathymetry images a complex pattern of folds and faults representing the surface expression of the crustal-scale Santa Maria splay-fault system. We modeled surface deformation using two different structural scenarios: deep-reaching normal faults and deep-reaching reverse faults with shallow extensional structures. Our preferred model comprises a blind reverse fault extending from 3km depth down to the plate interface at 16km that slips at a rate between 3.0 and 3.7m/ka. If all the splay-fault slip occurs during every great megathrust earthquake, with a recurrence of similar to 150-200years, the fault would slip similar to 0.5m per event, equivalent to a magnitude similar to 6.4 earthquake. However, if the splay-fault slips only with a megathrust earthquake every similar to 1000years, the fault would slip similar to 3.7m per event, equivalent to a magnitude similar to 7.5 earthquake.}, language = {en} }