@article{WessonMelnickCisternasetal.2015, author = {Wesson, Robert L. and Melnick, Daniel and Cisternas, Marco and Moreno, Marcos and Ely, Lisa L.}, title = {Vertical deformation through a complete seismic cycle at Isla Santa Maria, Chile}, series = {Nature geoscience}, volume = {8}, journal = {Nature geoscience}, number = {7}, publisher = {Nature Publ. Group}, address = {New York}, issn = {1752-0894}, doi = {10.1038/NGEO2468}, pages = {547 -- U157}, year = {2015}, abstract = {Individual great earthquakes are posited to release the elastic strain energy that has accumulated over centuries by the gradual movement of tectonic plates(1,2). However, knowledge of plate deformation during a complete seismic cycle-two successive great earthquakes and the intervening interseismic period-remains incomplete(3). A complete seismic cycle began in south-central Chile in 1835 with an earthquake of about magnitude 8.5 (refs 4,5) and ended in 2010 with a magnitude 8.8 earthquake(6). During the first earthquake, an uplift of Isla Santa Maria by 2.4 to 3m was documented(4,5). In the second earthquake, the island was uplifted(7) by 1.8 m. Here we use nautical surveys made in 1804, after the earthquake in 1835 and in 1886, together with modern echo sounder surveys and GPS measurements made immediately before and after the 2010 earthquake, to quantify vertical deformation through the complete seismic cycle. We find that in the period between the two earthquakes, Isla Santa Maria subsided by about 1.4 m. We simulate the patterns of vertical deformation with a finite-element model and find that they agree broadly with predictions from elastic rebound theory(2). However, comparison with geomorphic and geologic records of millennial coastline emergence(8,9) reveal that 10-20\% of the vertical uplift could be permanent.}, 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} } @article{LiMorenoRosenauetal.2014, author = {Li, Shaoyang and Moreno, Marcos and Rosenau, Matthias and Melnick, Daniel and Oncken, Onno}, title = {Splay fault triggering by great subduction earthquakes inferred from finite element models}, series = {Geophysical research letters}, volume = {41}, journal = {Geophysical research letters}, number = {2}, publisher = {American Geophysical Union}, address = {Washington}, issn = {0094-8276}, doi = {10.1002/2013GL058598}, pages = {385 -- 391}, year = {2014}, abstract = {We have investigated the influence that megathrust earthquake slip has on the activation of splay faults using a 2-D finite element method (FEM), taking into account the effects of gravity and variations in the frictional strength properties of splay faults. We simulated both landward-dipping and seaward-dipping splay fault geometries, and imposed depth-variable slip distributions of subduction events. Our results indicate that the two types of splay fault exhibit a similar behavior, with variations in frictional properties along the faults affecting only the seismic magnitude. The triggering process is controlled by a critical depth. Megathrust slip concentrated at depths shallower than the critical depth will favor normal displacement, while megathrust slip concentrated at depths deeper than the critical depth is likely to result in reverse motion. Our results thus provide a useful tool for predicting the activation of secondary faults and may have direct implications for tsunami hazard research.}, language = {en} } @unpublished{MelnickMorenoMotaghetal.2013, author = {Melnick, Daniel and Moreno, Marcos and Motagh, Mahdi and Cisternas, Marco and Wesson, Robert L.}, title = {Splay fault slip during the M-w 8.8 2010 maule Chile earthquake reply}, series = {Geology}, volume = {41}, journal = {Geology}, number = {12}, publisher = {American Institute of Physics}, address = {Boulder}, issn = {0091-7613}, doi = {10.1130/G34825Y.1}, pages = {E310 -- E310}, year = {2013}, language = {en} } @article{MelnickMorenoMotaghetal.2012, author = {Melnick, Daniel and Moreno, Marcos and Motagh, Mahdi and Cisternas, Marco and Wesson, Robert L.}, title = {Splay fault slip during the M-w 8.8 2010 Maule Chile earthquake}, series = {Geology}, volume = {40}, journal = {Geology}, number = {3}, publisher = {American Institute of Physics}, address = {Boulder}, issn = {0091-7613}, doi = {10.1130/G32712.1}, pages = {251 -- 254}, year = {2012}, abstract = {Splay faults are thrusts that emerge from the plate boundaries of subduction zones. Such structures have been mapped at several convergent margins and their activity commonly ascribed to large megathrust earthquakes. However, the behavior of splay faults during the earthquake cycle is poorly constrained because typically these structures are located offshore and are difficult to access. Here we use geologic mapping combined with space and land geodesy, as well as offshore sonar data, to document surface-fault ruptures and coastal uplift at Isla Santa Maria in south-central Chile (37 degrees S) caused by the 27 February 2010 Maule earthquake (M-w 8.8). During the earthquake, the island was tilted parallel to the margin, and normal faults ruptured the surface and adjacent ocean bottom. We associate tilt and crestal normal faulting with growth of an anticline above a blind reverse fault rooted in the Nazca-South America plate boundary, which slipped during the Maule earthquake. The splay fault system has formed in an area of reduced coseismic plate-boundary slip, suggesting that anelastic deformation in the upper plate may have restrained the 2010 megathrust rupture. Surface fault breaks were accompanied by prominent discharge of fluids. Our field observations support the notion that splay faulting may frequently complement and influence the rupture of subduction-zone earthquakes.}, language = {en} } @article{PenaHeidbachMorenoetal.2019, author = {Pena, Carlos and Heidbach, Oliver and Moreno, Marcos and Bedford, Jonathan and Ziegler, Moritz 0. and Tassara, Andres Ollero and Oncken, Onno}, title = {Role of Lower Crust in the Postseismic Deformation of the 2010 Maule Earthquake: Insights from a Model with Power-Law Rheology}, series = {Pure and applied geophysics}, volume = {176}, journal = {Pure and applied geophysics}, number = {9}, publisher = {Springer}, address = {Basel}, issn = {0033-4553}, doi = {10.1007/s00024-018-02090-3}, pages = {3913 -- 3928}, year = {2019}, abstract = {The surface deformation associated with the 2010 M-w 8.8 Maule earthquake in Chile was recorded in great detail before, during and after the event. The high data quality of the continuous GPS (cGPS) observations has facilitated a number of studies that model the postseismic deformation signal with a combination of relocking, afterslip and viscoelastic relaxation using linear rheology for the upper mantle. Here, we investigate the impact of using linear Maxwell or power-law rheology with a 2D geomechanical-numerical model to better understand the relative importance of the different processes that control the postseismic deformation signal. Our model results reveal that, in particular, the modeled cumulative vertical postseismic deformation pattern in the near field (< 300 km from the trench) is very sensitive to the location of maximum afterslip and choice of rheology. In the model with power-law rheology, the afterslip maximum is located at 20-35 km rather than > 50 km depth as suggested in previous studies. The explanation for this difference is that in the model with power-law rheology the relaxation of coseismically imposed differential stresses occurs mainly in the lower crust. However, even though the model with power-law rheology probably has more potential to explain the vertical postseismic signal in the near field, the uncertainty of the applied temperature field is substantial, and this needs further investigations and improvements.}, language = {en} } @article{MelnickCisternasMorenoetal.2012, author = {Melnick, Daniel and Cisternas, Marco and Moreno, Marcos and Norambuena, Ricardo}, title = {Estimating coseismic coastal uplift with an intertidal mussel calibration for the 2010 Maule Chile earthquake (M-w=8.8)}, series = {Quaternary science reviews : the international multidisciplinary research and review journal}, volume = {42}, journal = {Quaternary science reviews : the international multidisciplinary research and review journal}, number = {5}, publisher = {Elsevier}, address = {Oxford}, issn = {0277-3791}, doi = {10.1016/j.quascirev.2012.03.012}, pages = {29 -- 42}, year = {2012}, abstract = {Coseismic coastal uplift has been quantified using sessile intertidal organisms after several great earthquakes following FitzRoy's pioneer measurements in 1835. A dense survey of such markers may complement space geodetic data to obtain an accurate distribution of fault slip and earthquake segmentation. However, uplift estimates based on diverse intertidal organisms tend to differ, because of few methodological and comparative studies. Here, we calibrate and estimate coastal uplift in the southern segment of the 2010 Maule, Chile earthquake (M-w = 8.8) using > 1100 post-earthquake elevation measurements of the sessile mussel Perumytilus purpuratus. This mussel is the predominant competitor for rocky shores all along the Pacific coast of South America, where it forms fringes or belts distinctively in the middle intertidal zone. These belts are centered at mean sea level and their width should equal one third of the tidal range. We measured belt widths close to this value at 40\% of the sites, but overall widths are highly variable due to the unevenness in belt tops; belt bases, in turn, are rather regular. Belt top unevenness apparently results from locally-enhanced wave splash, whereas belt base evenness is controlled by predation. According to our measurements made beyond the earthquake rupture, the belt base is at the bottom of the middle intertidal zone, and thus we propose to estimate coastal uplift using the belt base mean elevation plus one sixth of the tidal range to reach mean sea level. Within errors our estimates agree with GPS displacements but differ from other methods. Comparisons of joint inversions for megathrust slip suggest combining space geodetic data with estimates from intertidal organisms may locally increase the detail of slip distributions.}, language = {en} } @article{MelnickMorenoCisternasetal.2012, author = {Melnick, Daniel and Moreno, Marcos and Cisternas, Marco and Tassara, Andres}, title = {Darwin seismic gap closed by the 2010 Maule earthquake}, series = {Andean geology}, volume = {39}, journal = {Andean geology}, number = {3}, publisher = {Servicio Nacional de Geolog{\`i}a y Miner{\`i}a}, address = {Santiago}, issn = {0718-7092}, doi = {10.5027/andgeoV39n3-a11}, pages = {558 -- 563}, year = {2012}, abstract = {The Maule earthquake (Mw 8.8) that affected south-central Chile on February 27, 2010 was preceded by the 1835 event documented by FitzRoy and Darwin. The relation between both events has been controversial. Fault slip in 2010 estimated by Lorito et al. (2011) is less than expected from 175 years of strain accumulation, leading them to conclude only limited overlap between the 2010 and 1835 events, and that a Mw 7.5-8 event could still strike the Concepcion region. However, Lorito et al.'s model was based on displacements obtained from only 6 GPS stations and underpredicts observations from recent studies. Here we show that an alternative model based on 169 GPS displacements reproduces the data better, suggesting Lorito et al.'s main conclusion is not correct. Based on a slip deficit map, we suggest the seismic gap opened in 1835 was most likely closed in 2010.}, language = {en} } @article{MelnickLiMorenoetal.2018, author = {Melnick, Daniel and Li, Shaoyang and Moreno, Marcos and Cisternas, Marco and Jara-Munoz, Julius and Wesson, Robert and Nelson, Alan and Baez, Juan Carlos and Deng, Zhiguo}, title = {Back to full interseismic plate locking decades after the giant 1960 Chile earthquake}, series = {Nature Communications}, volume = {9}, journal = {Nature Communications}, publisher = {Nature Publ. Group}, address = {London}, issn = {2041-1723}, doi = {10.1038/s41467-018-05989-6}, pages = {10}, year = {2018}, abstract = {Great megathrust earthquakes arise from the sudden release of energy accumulated during centuries of interseismic plate convergence. The moment deficit (energy available for future earthquakes) is commonly inferred by integrating the rate of interseismic plate locking over the time since the previous great earthquake. But accurate integration requires knowledge of how interseismic plate locking changes decades after earthquakes, measurements not available for most great earthquakes. Here we reconstruct the post-earthquake history of plate locking at Guafo Island, above the seismogenic zone of the giant 1960 (M-w = 9.5) Chile earthquake, through forward modeling of land-level changes inferred from aerial imagery (since 1974) and measured by GPS (since 1994). We find that interseismic locking increased to similar to 70\% in the decade following the 1960 earthquake and then gradually to 100\% by 2005. Our findings illustrate the transient evolution of plate locking in Chile, and suggest a similarly complex evolution elsewhere, with implications for the time- and magnitude-dependent probability of future events.}, language = {en} } @article{LangeTilmannBarrientosetal.2012, author = {Lange, Dietrich and Tilmann, Frederik and Barrientos, Sergio E. and Contreras-Reyes, Eduardo and Methe, Pascal and Moreno, Marcos and Heit, Ben and Agurto, Hans and Bernard, Pascal and Vilotte, Jean-Pierre and Beck, Susan}, title = {Aftershock seismicity of the 27 February 2010 Mw 8.8 Maule earthquake rupture zone}, series = {Earth \& planetary science letters}, volume = {317}, journal = {Earth \& planetary science letters}, number = {2}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0012-821X}, doi = {10.1016/j.epsl.2011.11.034}, pages = {413 -- 425}, year = {2012}, abstract = {On 27 February 2010 the M-w 8.8 Maule earthquake in Central Chile ruptured a seismic gap where significant strain had accumulated since 1835. Shortly after the mainshock a dense network of temporary seismic stations was installed along the whole rupture zone in order to capture the aftershock activity. Here, we present the aftershock distribution and first motion polarity focal mechanisms based on automatic detection algorithms and picking engines. By processing the seismic data between 15 March and 30 September 2010 from stations from IRIS, IPGP, GFZ and University of Liverpool we determined 20,205 hypocentres with magnitudes M-w between 1 and 5.5. Seismic activity occurs in six groups: 1.) Normal faulting outer rise events 2.) A shallow group of plate interface seismicity apparent at 25-35 km depth and 50-120 km distance to the trench with some variations between profiles. Along strike, the aftershocks occur largely within the zone of coseismic slip but extend similar to 50 km further north, and with predominantly shallowly dipping thrust mechanisms. Along dip, the events are either within the zone of coseismic slip, or downdip from it, depending on the coseismic slip model used. 3.) A third band of seismicity is observed further downdip at 40-50 km depth and further inland at 150-160 km trench perpendicular distance, with mostly shallow dipping (similar to 28 degrees) thrust focal mechanisms indicating rupture of the plate interface significantly downdip of the coseismic rupture, and presumably above the intersection of the continental Moho with the plate interface. 4.) A deep group of intermediate depth events between 80 and 120 km depth is present north of 36 degrees S. Within the Maule segment, a large portion of events during the inter-seismic phase originated from this depth range. 5.) The magmatic arc exhibits a small amount of crustal seismicity but does not appear to show significantly enhanced activity after the M-w 8.8 Maule 2010 earthquake. 6.) Pronounced crustal aftershock activity with mainly normal faulting mechanisms is found in the region of Pichilemu (similar to 34.5 degrees S). These crustal events occur in a similar to 30 km wide region with sharp inclined boundaries and oriented oblique to the trench. The best-located events describe a plane dipping to the southwest, consistent with one of the focal planes of the large normal-faulting aftershock (M-w = 6.9) on 11 March 2010.}, language = {en} }