TY - JOUR A1 - Vargas, Gabriel A1 - Farias, Marcelo A1 - Carretier, Sebastien A1 - Tassara, Andres A1 - Baize, Stephane A1 - Melnick, Daniel T1 - Coastal uplift and tsunami effects associated to the 2010 M(w)8.8 Maule earthquake in Central Chile JF - Andean geology N2 - On February 27, 2010 at 03:34:08 AM an M(w)8.8 earthquake, with epicenter located off Cobquecura (73.24 degrees W; 36.29 degrees S), severely hit Central Chile. The tsunami waves that followed this event affected the coastal regions between the cities of Valparaiso and Valdivia, with minor effects as far as Coquimbo. The earthquake occurred along the subduction of the Nazca oceanic plate beneath the South American plate. Coseismic coastal uplift was estimated through observations of bleached lithothamnioids crustose coralline algae, which were exposed after the mainshock between 34.13 degrees S and 38.34 degrees S, suggesting the latitudinal distribution of the earthquake rupture. The measured coastal uplift values varied between 240 +/- 20 cm at sites closer to the trench along the western coast of the Arauco peninsula and 15 +/- 10 cm at sites located farther east. A maximum value of 260 +/- 50 cm was observed at the western coast of Santa Maria Island, which is similar to the reported uplift associated with the 1835 earthquake at Concepcion. Land subsidence values on the order of 0.5 m to 1 m evidenced a change in polarity and position of the coseismic hinge at 110-120 km from the trench. In four sites along the coast we observed a close match between coastal uplift values deduced from bleached lithothamnioids algae and GPS measurements. According to field observations tsunami heights reached ea. 14 m in the coastal area of the Maule Region immediately north of the epicenter, and diminished progressively northwards to 4-2 m near Valparaiso. Along the coast of Cobquecura, tsunami height values were inferior to 2-4 m. More variable tsunami heights of 6-8 m were measured at Dichato-Talcahuano and Tirua-Puerto Saavedra, in the Biobio and Arauco regions, respectively, to the south of the epicenter. According to eyewitnesses, the tsunami reached the coast between 12 to 20 and 30 to 45 minutes in areas located closer and faraway from the earthquake rupture zone, respectively. Destructive tsunami waves arrived also between 2.5 and 4.5 hours after the mainshock, especially along the coast of the Biobio and Arauco regions. The tsunami effects were highly variable along the coast, as a result of geomorphological and bathymetric local conditions, besides potential complexities induced by the main shock. KW - M(w)8.8 Maule earthquake KW - Central Chile KW - Coseismic coastal uplift KW - Tsunami effect Y1 - 2011 U6 - https://doi.org/10.5027/andgeoV38n1-a12 SN - 0718-7106 VL - 38 IS - 1 SP - 219 EP - 238 PB - Servicio Nacional de Geologìa y Minerìa CY - Santiago ER - TY - JOUR A1 - Melnick, Daniel A1 - Hillemann, Christian A1 - Jara Muñoz, Julius A1 - Garrett, Ed A1 - Cortes-Aranda, Joaquin A1 - Molina, Diego A1 - Tassara, Andrés A1 - Strecker, Manfred T1 - Hidden Holocene Slip Along the Coastal El Yolki Fault in Central Chile and Its Possible Link With Megathrust Earthquakes JF - Journal of geophysical research : Solid earth N2 - Megathrust earthquakes are commonly accompanied by increased upper-plate seismicity and occasionally triggered fault slip. In Chile, crustal faults slipped during and after the 2010 Maule (M8.8) earthquake. We studied the El Yolki fault (EYOF), a transtensional structure midways the Maule rupture not triggered in 2010. We mapped a Holocene coastal plain using light detection and ranging, which did not reveal surface ruptures. However, the inner-edge and shoreline angles along the coastal plain as well as 4.3- to 4.0-ka intertidal sediments are back-tilted on the EYOF footwall block, documenting 10 m of vertical displacement. These deformed markers imply similar to 2-mm/year throw rate, and dislocation models a slip rate of 5.6 mm/year for the EYOF. In a 5-m-deep trench, the Holocene intertidal sediments onlap to five erosive steps, interpreted as staircase wave-cut landforms formed by discrete events of relative sea level drop. We tentatively associated these steps with coseismic uplift during EYOF earthquakes between 4.3 and 4.0 ka. The Maule earthquake rupture may be subdivided into three subsegments based on coseismic slip and gravity anomalies. Coulomb stress transfer models predict neutral stress changes at the EYOF during the Maule earthquake but positive changes for a synthetic slip distribution at the central subsegment. If EYOF earthquakes were triggered by megathrust events, their slip distribution was probably focused in the central subsegment. Our study highlights the millennial variability of crustal faulting and the megathrust earthquake cycle in Chile, with global implications for assessing the hazards posed by hidden but potentially seismogenic coastal faults along subduction zones. KW - Central Chile KW - megathrust earthquake KW - crustal fault KW - seismotectonic segmentation KW - Middle Holocene KW - sea level change Y1 - 2019 U6 - https://doi.org/10.1029/2018JB017188 SN - 2169-9313 SN - 2169-9356 VL - 124 IS - 7 SP - 7280 EP - 7302 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Lange, Dietrich A1 - Tilmann, Frederik A1 - Barrientos, Sergio E. A1 - Contreras-Reyes, Eduardo A1 - Methe, Pascal A1 - Moreno, Marcos A1 - Heit, Ben A1 - Agurto, Hans A1 - Bernard, Pascal A1 - Vilotte, Jean-Pierre A1 - Beck, Susan T1 - Aftershock seismicity of the 27 February 2010 Mw 8.8 Maule earthquake rupture zone JF - Earth & planetary science letters N2 - 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. KW - Maule 2010 earthquake KW - local seismicity KW - aftershock distribution KW - subduction zone KW - Central Chile KW - seismogenic zone Y1 - 2012 U6 - https://doi.org/10.1016/j.epsl.2011.11.034 SN - 0012-821X VL - 317 IS - 2 SP - 413 EP - 425 PB - Elsevier CY - Amsterdam ER -