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We study the deep structure of the continental wedge along the south‐central Chilean convergent margin based on a joint interpretation of wide‐angle reflection and refraction seismic phases acquired between the southern part of the Maule 2010 (36°S) and the northern part of the Valdivia 1960 (41°S) earthquake rupture areas. When combined with results of previous seismic studies, our results provide new insights into the deep structure (to 15–20 km) of the overriding, continental South American plate. We observe a latitudinal variation of P wave velocity, interpreted in terms of the distribution of Permo‐Triassic metamorphic complex near the coast, and deep reflectors at the base of these metamorphic units. A change in the observed deep structural style near 38°S suggests a segmentation in the interplate frictional properties between the Maule and Valdivia earthquakes rupture zones. This regional change in the continental wedge structure indicates a spatial correlation between the coseismic ruptures of large earthquakes (e.g., the 1960 and 2010 megathrust earthquakes) and the rheology/lithology along the interplate boundary. Plain Language Summary: Recent studies suggest that upper plate structure plays a key role during large earthquakes in subduction zones. This work presents the interpretation of 2D seismic velocity models and the analysis of seismic waves reflected in the deep zone of the continental crust, obtained along the south‐central Chilean subduction zone (between 36°S and 41°S). This zone includes the southern portion of the Mw8.8 Maule earthquake (2010) and the northern patch of the Mw9.6 Valdivia earthquake (1960). Seismic data were acquired during the NSF‐CEVICHE (Crustal Experiment from Valdivia to Illapel to Characterize Huge Earthquakes) cruise by the American R/V Marcus Langseth in January/February 2017 and by seismometers deployed onshore. The data processing and interpretation are complemented by previous seismic information in the area. We observe a variation of seismic structure along the margin, interpreted in terms of the distribution of Permo‐Triassic metamorphic units. The change in the observed deep structural style suggests differences in the frictional properties between the tectonic plates in the zones where the Maule and Valdivia earthquakes ruptured. Results highlight that a physical characterization of the continental wedge and the study of its geological evolution provides a necessary framework for understanding the complexities of large subduction earthquakes. Key Points: A middle continental wedge unit of relatively high Vp is interpreted as the seaward continuation of the Permo‐Triassic metamorphic complexObserved deep reflectors show the presence of structures at the base of the Permo‐Triassic metamorphic complexA change in the deep structural style, near 38°S, suggests a segmentation in the interplate frictional properties [ABSTRACT FROM AUTHOR]

The characteristics of the short-period S-wave attenuation field in the source zone of the strongest Tohoku earthquake of March 11, 2011 in the northeast of Japan are considered (Mw = 9.0). The records of shallow local earthquakes obtained by the MAJO station at distances of 250 to 700 km are processed. A method based on the analysis of the ratio of the maximum amplitudes of the Sn and Pn waves (the Sn/Pn parameter) is used. The source zone is divided into four regions bounded by coordinates 36°–37°, 37°–38°, 38°–39°, and 39°–40°18′ N; and 140°30ʹ–145° E. It is established that all the regions contain segments of a rapid decrease in the Sn/Pn values, which are followed by segments of their sharp growth at small epicentral distances in all the areas. Another segment of rapid decrease in the Sn/Pn parameter is identified in all regions at relatively large distances. It is assumed that the first segments of rapid decrease in the Sn/Pn values are related to the gradual sinking of the S-wave rays in the mantle wedge. In this case, the minimum values of the parameter correspond to rays partly moving along the foot of this wedge. Such an effect is explained by the fact that the biggest content of the deep-seated fluids ascending due to the dehydration of the oceanic crust rocks correspond to the bottom of the mantle wedge. The segments of a sharp increase in the Sn/Pn values are likely to correspond to the propagation of rays within the upper part of the plate characterized by very weak attenuation. The second segments of the rapid decrease in the Sn/Pn parameter are related to the ray penetration into the waveguide formed in the bottom part of the plate formed as a result of the dehydration of the mantle rocks. The mean values Sn/Pn(Δ) in the four areas are much lower than in the source zone of the strongest Maule earthquake of February 27, 2010 (Chile, Mw = 8.8). This effect agrees with the earlier assumption about the larger fluid content in the subduction zones in the west of the Pacific Ocean compared to the east. Furthermore, this allows us to explain the features of the aftershock processes in these two enormous regions of the Pacific Ring. [ABSTRACT FROM AUTHOR]

A conceptual proposal of the profiles and roles that communicators can assume during the coverage of a disaster was developed based on the discourse analysis of the interventions made by the anchorpersons of the Chilean broadcast TV newscasts during the 8.8 Mw earthquake of 2010. This was used to identify and describe the presence of three potential profiles: informative (descriptive presentation of the content), judgmental (a judgment position prevails), and of dialogue with the audience (direct message to viewers). The data shows that the predominant profile was the informative one, whereas the judgmental appears strongly during the first days of disaster and then weakens, and that the dialogue with the audience is strengthened from the third day. These results open a line of research on the role of the media to promote the spontaneous recovery of a population faced with a trauma. [ABSTRACT FROM AUTHOR]

Throughout history people have been affected by disaster events such as earthquakes, tsunamis, floods and landslides, with devastating effects for cities and towns around the world. Since the 1990s, post-disaster reconstruction has often been seen as an opportunity to invest in new projects following market forces and property speculation rather than for implementing rehabilitation strategies to address physical, social and psychological effects. Housing subsidies provided by the government seem to be a new issue creating more social disparity in the case of Talca, Chile after the 2010 magnitude 8.8 earthquake. This paper explores the contemporary urban landscape of this intermediate city, shaped between 2010 and 2016, which shows a great number of empty plots being filled by gated community typologies. By using ethnography and semi-structured interviews of residents from four historic neighbourhoods, the results show key patterns of physical and social change such as displacement of original residents by newcomers and lack of social cohesion along with tensions among them. The case of the Talca, Chile reconstruction is educational for understanding the ways in which many inner cities are affected by reconstruction policies with property speculation and gentrification effects. This paper concludes with the criteria that are being applied to redesign historic neighbourhoods and provides reflections for improving urban planning mechanisms to include both original residents and newcomers who are sharing these historic neighbourhoods. [ABSTRACT FROM AUTHOR]

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 ~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. Key Points: Geomorphology and paleoseismic trenching suggest Holocene slip along El Yolki fault in Central Chile despite absence of surface rupturesA 4.3‐ka sequence of intertidal sediments has been uplifted ~10 m along the footwall fault blockCrustal faulting may be triggered by megathrust events with slip distribution different from the last M8.8 earthquake in 2010 [ABSTRACT FROM AUTHOR]

We address the question of whether all large‐magnitude earthquakes produce an erosion peak in the subaerial components of fluvial catchments. We evaluate the sediment flux response to the Maule earthquake in the Chilean Andes (Mw 8.8) using daily suspended sediment records from 31 river gauges. The catchments cover drainage areas of 350 to around 10,000 km2, including a wide range of topographic slopes and vegetation cover of the Andean western flank. We compare the 3‐ to 8‐year postseismic record of sediment flux to each of the following preseismic periods: (1) all preseismic data, (2) a 3‐year period prior to the seismic event, and (3) the driest preseismic periods, as drought conditions prevailed in the postseismic period. Following the earthquake, no increases in suspended sediment flux were observed for moderate to high percentiles of the streamflow distribution (mean, median, and ≥75th percentile). However, more than half of the examined stations showed increased sediment flux during baseflow. By using a Random Forest approach, we evaluate the contributions of seismic intensities, peak ground accelerations, co‐seismic landslides, hydroclimatic conditions, topography, lithology, and land cover to explain the observed changes in suspended sediment concentration and fluxes. We find that the best predictors are hillslope gradient, low‐vegetation cover, and changes in streamflow discharge. This finding suggests a combined first‐order control of topography, land cover, and hydrology on the catchment‐wide erosion response. We infer a reduced sediment connectivity due to the postseismic drought, which increased the residence time of sediment detached and remobilized following the Maule earthquake. Key Points: Postseismic suspended sediment fluxes decreased during moderate‐ to high‐flow conditions with respect to background valuesA reduced hillslope‐channel connectivity due to drought and limited coseismic landsliding set the catchment‐wide erosive responseDuring postseismic dry conditions, the first‐order control on catchment‐wide erosion is the combined effect of topography and land cover [ABSTRACT FROM AUTHOR]

Abstract Toxic metal content were measured in samples of mollusc Concholepas concholepas obtained from the Chilean coast. Samples were collected during two periods, one before and one after the earthquake-tsunami which occurred in the Maule Region, Chile, February 27th, 2010 as a result of an earthquake with a magnitude of 8.8. Quantification of toxic metals in samples of hepatopancreas and muscle tissue was performed using flame atomic absorption spectroscopy. The analytical methodology was validated with certified reference material. The content means measured in muscle tissue for January 2010 were Cu: 10.3; Cr: 0.7; Cd: < 0.1; Mn: 3.6 and Zn: 38.6 µg g−1 (dry weight). For October 2014, the means were Cu: 8; Cr: 2.4; Cd: < 0.1; Mn: 5.6 and Zn: 45.4 µg g−1 (dry weight). In hepatopancreas tissue, the content means were Cu: 14.8; Cr: 2.4; Cd: 246.2; Mn: 4.4 and Zn: 1552.9 µg g−1 (dry weight). For October 2014, the means were Cu: 53.7; Cr: 3.5; Cd: 118; Mn: 13.4 and Zn: 1352.3 µg g−1 (dry weight). Cd, Cr, Cu, Mn and Zn content in the samples of hepatopancreas were generally higher than those recorded in muscle tissue however they were not always statistically significant. Statistical analysis showed that Cu and Mn content in the post-tsunami period increased in the hepatopancreas tissue. The concentrations of Cd, Cr, Cu, Mn, and Zn measured in the muscular tissue (edible part) of the species Conchalepas concholepas, were lower than the maximum contents allowed by the current legislation (FAO/WHO, 2004; EU, 2001) and its consumption is not a risk to human health. Graphical abstract fx1 Highlights • Heavy metals are not degraded in nature by biological or chemical processes distances. • Earthquakes and tsunamis produce great movements of marine sediments, which contain high levels of heavy metals. • The concentrations of heavy metals in muscle were generally lower than those found in the hepatopancreas of each specimen. • The increases in the concentrations of Cr, Mn and Cu after the tsunami may be to the stirring up of marine sediments. [ABSTRACT FROM AUTHOR]

Highlights • First high-resolution data from a creepmeter array collocated with seismometers. • Monitored faults are highly susceptible to dynamically triggered shallow slip. • Far-field triggering relates to surface waves, near-field triggering to body waves. • Large earthquakes can trigger shallow slip events over distances of 103–105 km. • Triggered shallow slip scales with seismic energy density. Abstract The M w = 8.8 Maule Earthquake of February 27, 2010, remotely triggered minor surface displacement along the Atacama Fault System in Northern Chile located 1500–1800 km from the epicenter. Here we present evidence that surface displacement events recorded by the IPOC (Integrated Plate Boundary Observatory in N-Chile) Creepmeter Array are related to earthquakes on the underlying subduction zone interface or to large earthquakes around the world. Our observations document dynamic triggering of shallow slip on faults in a forearc setting. Continuous monitoring revealed that up to 30 displacement events per year occur on the monitored fault segments, >90% of them triggered by earthquakes in the near or far field synchronous to the passage of the seismic wave. We can clearly attribute far field triggering to the passage of the surface wave and near field triggering to the passage of the body wave. The most distant triggered displacement event monitored occurred after the 2011, M w = 9.0 Tohoku-Oki Earthquake located 16 468 km away following the passage of large amplitude SS waves. Comparing the triggered displacement events with other triggered phenomena like seismicity, volcanic eruptions, hydrological changes as well as with data from the California Creepmeter Array we find that the seismic energy density appropriately describes a magnitude–distance scaling relationship of slip triggering. Finally, the observed surface displacement is found to not occur by continuous creep, but rather through nearly exclusively discrete displacement events. [ABSTRACT FROM AUTHOR]

Postseismic displacements following great subduction earthquakes show significant long‐wavelength and time‐dependent patterns caused primarily by transient viscoelastic relaxation processes occurring broadly at depth. However, the Earth's viscosity structure and time‐dependent variations are still poorly understood, especially in the years immediately following a great earthquake. Here we investigate the spatiotemporal variation of mantle viscosity proximal and distal to the southern Andes using 8 years of continuous high‐resolution GPS observations following the 2010 Mw 8.8 Maule earthquake in south Central Chile. We remove the potential influences of relocking and afterslip on far‐field GPS displacements and estimate viscosities that can explain the 3‐D displacements. The optimal viscosity structure exhibits a low‐viscosity (~1018Pa s) mantle beneath the Andean volcanic arc and high‐viscosity (>1022Pa s) cratonic mantle, indicating a dependence of transient viscosity on temperature. Comparisons of the viscosity distributions at different times show that mantle viscosities increase with time throughout the study region. Viscosity increase is generally fastest in the mantle wedge beneath the Andes and slows down with increasing distance from the source region of the Maule earthquake. Such temporal viscosity evolution may indicate a stress dependence of the viscosity proximal to the rupture zone, while regions east of the Andes act as a relatively rigid body (i.e., cratonic mantle) with much higher viscosity. Our results thus suggest that both temperature structure and stress state contribute to spatiotemporal variations of the mantle viscosity. Heterogeneous spatiotemporal variations of viscosity seem to control the expansion and duration of the postseismic deformation and therefore the postseismic stress evolution. Plain Language Summary: We used continuous GPS positioning data to study the viscosity distribution at depth and its time variation following the 2010 Mw 8.8 Maule, Chile, earthquake. We find that the viscosities in the volcanic/mountain range regions, where deep rocks are expected hot, are relatively low (i.e., the materials are in weak state prone to flow easily), while the viscosities in far regions, where an ancient cold crust is expected, are relatively high (i.e., the materials are too strong to flow). This finding can, therefore, be related to the temperature distribution at depth. Furthermore, we find that the viscosities in all regions except the region of ancient crust increase with time and the rate of viscosity recovery decreases with the distance to the earthquake location. This phenomenon can, therefore, be related to the earthquake‐induced stresses. Another interesting thing found in this study is that the ancient crust is likely not influenced much by the earthquake and behaves very strong in all the observation time. In all, we propose that both temperature and earthquake stresses control the rock strengths following a great earthquake. This study thus contributes to our understanding of the stress evolution at depth through the earthquake cycle and hence mechanisms of the earthquake happening. Key Points: Eight years of continuous GPS observations following the 2010 Maule, Chile, earthquake show intriguing spatiotemporal deformation patternIn the proximal area, between 300 and 700 km from the trench, the viscosity is temperature and stress dependent inferred from modelingIn the distal area, between 700 and ~1,400 km, a highly viscous cratonic mantle is inferred [ABSTRACT FROM AUTHOR]

A network is given whose edges need to be constructed (or restored after a disaster). The lengths of edges represent the required construction/restoration times given available resources, and one unit of length of the network can be constructed per unit of time. All points of the network are accessible for construction at any time. For each pair of vertices, a due date is given. It is required to find a construction schedule that minimizes the maximum lateness of all pairs of vertices, where the lateness of a pair is the difference between the time when the pair becomes connected by an already constructed path and the pair's due date.We introduce the problem and analyze its structural properties, present a mixed-integer linear programming formulation, develop a number of lower bounds that are integrated in a branch-and-bound algorithm, and discuss results of computational experiments both for instances based on randomly generated networks and for instances based on 2010 Chilean earthquake data. [ABSTRACT FROM AUTHOR]

This paper examines changes in gender relations in a small coastal community as a result of the 2010 Chile earthquake and tsunami. Vulnerability and resilience are used as a conceptual framework to analyse these changes. Based on empirical evidence from a seven-year longitudinal study and quasi-ethnographic work, we explore changes in power relations at the different stages of the disaster and longer-term recovery as well as the conditions that fostered these changes. Our findings show distinct patterns of change. First, disasters can trigger long-lasting changes that challenge historical patriarchal relations. Second, while vulnerability increases following a disaster, resilience can potentially counteract women’s vulnerability. We propose that resilience can be a pathway to produce long-term changes in gender relations and empower women in the context of disasters. [ABSTRACT FROM AUTHOR]

This research examines the level of citizen satisfaction for the housing solution provided during the reconstruction process, after the Chile earthquake and tsunami, on 27 February 2010, in Dichato Bay, through a multidisciplinary approach. This implied, on the one hand, the application of a survey aimed at determining the level of agreement or disagreement with the reconstruction programme; and, on the other hand, an architectural and urban study, based on an analysis of the planimetric design and the location of the housing received by the beneficiaries, to outline the relation between the fulfilment of technical aspects and the social perception of satisfaction. The main results reflect a positive regard for the reconstruction plan, as well as a limited relation between the level of user satisfaction and the final housing solution provided. [ABSTRACT FROM AUTHOR]

Talca, Chile, has been negatively impacted by both a major 2010 earthquake and the ensuing reconstruction process. Talca’s poor have been forced out from their neighborhoods and relocated to remote areas where employment, public transportation, and basic services are limited. Based on extensive community development work in Talca, this article analyzes the dynamics that have led to these conditions and the insufficiently supported alternative community-based initiatives that could have allowed Talca to redevelop in more sustainable and equitable ways. Planners need to systemically understand the implications of programs often pushed in times of emergency as urgent and inevitable that may not favor a healthy long-term redevelopment of communities recovering from disasters, be politically savvy and courageous to denounce and resist them when necessary, and work with/for communities to define and promote more just and sustainable postdisaster futures. [ABSTRACT FROM AUTHOR]

This paper examines the impact of the 2010 Chile earthquake and tsunami on community resilience, and the crucial role that communities had to play in coping with this event. The results of a primary research conducted in Talcahuano, one of the worst affected cities by the disaster (through methods of semi-structured interviews, observation, documentary review and social media) show that communities have the power to activate internal resilience capacities to cope with and recover from natural disasters. For instance, the role of social networks, organisation, cooperation, trust, local knowledge, and participation was crucial at all stages of the disaster. The study highlights that communities are not simply passive victims of disasters; rather, they are active agents. The lessons from the 2010 Chile earthquake and tsunami can become a useful operational tool for managing efficiently emergency situations in vulnerable communities and planning effective and sustainable disaster risk reduction policies in developing countries. [ABSTRACT FROM AUTHOR]

We present a different view of secular variation of the Earth's magnetic field, through the variations in the threshold rigidity known as the variation rate of geomagnetic cutoff rigidity (VRc). As the geomagnetic cutoff rigidity (Rc) lets us differentiate between charged particle trajectories arriving at the Earth and the Earth's magnetic field, we used the VRc to look for internal variations in the latter, close to the 70° south meridian. Due to the fact that the empirical data of total magnetic field BF and vertical magnetic field Bz obtained at Putre (OP) and Los Cerrillos (OLC) stations are consistent with the displacement of the South Atlantic magnetic anomaly (SAMA), we detected that the VRc does not fully correlate to SAMA in central Chile. Besides, the lower section of VRc seems to correlate perfectly with important geological features, like the flat slab in the active Chilean convergent margin. Based on this, we next focused our attention on the empirical variations of the vertical component of the magnetic field Bz, recorded in OP prior to the Maule earthquake in 2010, which occurred in the middle of the Chilean flat slab. We found a jump in Bz values and main frequencies from 3.510 to 5.860µHz, in the second derivative of Bz, which corresponds to similar magnetic behavior found by other research groups, but at lower frequency ranges. Then, we extended this analysis to other relevant subduction seismic events, like Sumatra in 2004 and Tohoku in 2011, using data from the Guam station. Similar records and the main frequencies before each event were found. Thus, these results seem to show that magnetic anomalies recorded on different timescales, as VRc (decades) and Bz (days), may correlate with some geological events, as the lithosphere–atmosphere–ionosphere coupling (LAIC). [ABSTRACT FROM AUTHOR]

Earthquakes are a common and deadly natural disaster, with roughly one-quarter of survivors subsequently developing posttraumatic stress disorder (PTSD). Despite progress identifying risk factors, limited research has examined how to combine variables into an optimized post-earthquake PTSD prediction tool that could be used to triage survivors to mental health services. The current study developed a post-earthquake PTSD risk score using machine learning methods designed to optimize prediction. The data were from a two-wave survey of Chileans exposed to the 8.8 magnitude earthquake that occurred in February 2010. Respondents (n = 23,907) were interviewed roughly three months prior to and again three months after the earthquake. Probable post-earthquake PTSD was assessed using the Davidson Trauma Scale. We applied super learning, an ensembling machine learning method, to develop the PTSD risk score from 67 risk factors that could be assessed within one week of earthquake occurrence. The super learner algorithm had better cross-validated performance than the 39 individual algorithms from which it was developed, including conventional logistic regression. The super learner also had a better area under the receiver operating characteristic curve (0.79) than existing post-disaster PTSD risk tools. Individuals in the top 5%, 10%, and 20% of the predicted risk distribution accounted for 17.5%, 32.2%, and 51.4% of all probable cases of PTSD, respectively. In addition to developing a risk score that could be implemented in the near future, these results more broadly support the utility of super learning to develop optimized prediction functions for mental health outcomes. [ABSTRACT FROM AUTHOR]

The interpretation of multiannual satellite geodetic observations after the 2010 Maule earthquake is given on the basis of the keyboard concept of the subduction region structure. It is shown that this concept, combined with the models of viscoelastic relaxation in the asthenosphere and nonstationary convection system in the upper mantle, completely explains the surface displacements observed. [ABSTRACT FROM AUTHOR]

The Maule Earthquake (M w = 8.8) of February 27, 2010 is among the strongest earthquakes that occurred in recent years throughout the world. The crustal deformation caused by this earthquake has been widely studied using GNSS, InSAR and gravity observations. However, there is currently no estimation of the possible vertical deformations produced by co-seismic and post-seismic effects in segments of the Chilean Vertical Reference Frame (CHVRF). In this paper, we present an estimation of co-seismic and post-seismic deformations on the CHVRF using an indirect approach based on GNSS and Gravity Recovery and Climate Experiment (GRACE) data as well as by applying a trajectory model. GNSS time series were used from 10 continuous GNSS stations in the period from 2007 to 2015, as well as 28 GNSS temporary stations realized before and after the earthquake, and 34 vertical deformation vectors in the region most affected by the earthquake. We considered a set of 147 monthly solutions of spherical harmonic gravity field that were expanded up to degree, as well as order 96 of the GRACE mission provided by Center for Space Research, University of Texas at Austin (UT-CSR) process center. The magnitude of vertical deformation was estimated in part of the Chilean vertical network due to the co-seismic and post-seismic effects. Once we evaluated the hydrological effect, natural and artificial jumps, and the effect of glacial isostatic adjustment in GNSS and GRACE time series, the maximum values associated to co- and post-seismic deformations on orthometric height were found to be ∼−34 cm and 5 cm, respectively. Overall, the deformation caused by the Maule earthquake in orthometric heights is almost entirely explained by the variation in the ellipsoidal heights (over 85% in co-seismic jump); however, coseismic jump in the geoid reached −3.3 mm, and could influence the maintenance of a modern vertical reference network in a medium to long term. We evaluated the consistency for a segment of the CHVRF after the earthquake and recommended precautions for using the CHVRF in the region. [ABSTRACT FROM AUTHOR]

Intermedia agenda setting predicts a high degree of convergence between news media agendas. However, the rise of social media forces a re-examination of this expectation. Using the 8.8-earthquake of February 27, 2010 in Chile as a case study, this article compares which topics were covered by professional journalists on broadcast news and Twitter, analyzing both cross-sectional and longitudinal trends. A positive, reinforcing influence was found among the journalistic agendas of TV and Twitter. However, counter to the idea that social media are echo chambers of traditional media, it was found that Twitter influences TV news more so than the other way around. Thus, the study provides an early lens into the agenda setting function of social media among television news professionals, and its findings are consistent with Twitter succeeding among journalists due to its provision of valuable information. [ABSTRACT FROM AUTHOR]

Nonlinear finite element (FE) modeling has been widely used to investigate the effects of seismic isolation on the response of bridges to earthquakes. However, most FE models of seismic isolated bridges (SIB) have used seismic isolator models calibrated from component test data, while the prediction accuracy of nonlinear FE models of SIB is rarely addressed by using data recorded from instrumented bridges. In this paper, the accuracy of a state-of-the-art FE model is studied through nonlinear FE model updating (FEMU) of an existing instrumented SIB, the Marga-Marga Bridge located in Viña del Mar, Chile. The seismic isolator models are updated in 2 phases: component-wise and system-wise FEMU. The isolator model parameters obtained from 23 isolator component tests show large scatter, and poor goodness of fit of the FE-predicted bridge response to the 2010 Mw 8.8 Maule, Chile Earthquake is obtained when most of those parameter sets are used for the isolator elements of the bridge model. In contrast, good agreement is obtained between the FE-predicted and measured bridge response when the isolator model parameters are calibrated using the bridge response data recorded during the mega-earthquake. Nonlinear FEMU is conducted by solving single- and multiobjective optimization problems using high-throughput cloud computing. The updated FE model is then used to reconstruct response quantities not recorded during the earthquake, gaining more insight into the effects of seismic isolation on the response of the bridge during the strong earthquake. [ABSTRACT FROM AUTHOR]

Subduction megathrust earthquakes show complex rupture behaviour and large lateral variations of slip. However, the factors controlling seismic slip are still under debate. Here, we present 2-D velocity-depth tomographic models across four trench-perpendicular wide angle seismic profiles complemented with high resolution bathymetric data in the area of maximum coseismic slip of the M w 8.8 Maule 2010 megathrust earthquake (central Chile, 34°–36°S). Results show an abrupt lateral velocity gradient in the trench-perpendicular direction (from 5.0 to 6.0 km/s) interpreted as the contact between the accretionary prism and continental framework rock whose superficial expression spatially correlates with the slope-shelf break. The accretionary prism is composed of two bodies: (1) an outer accretionary wedge (5–10 km wide) characterized by low seismic velocities of 1.8–3.0 km/s interpreted as an outer frontal prism of poorly compacted and hydrated sediment, and (2) the middle wedge (∼50 km wide) with velocities of 3.0–5.0 km/s interpreted as a middle prism composed by compacted and lithified sediment. In addition, the maximum average coseismic slip of the 2010 megathrust event is fairly coincident with the region where the accretionary prism and continental slope are widest (50–60 km wide), and the continental slope angle is low (<5°). We observe a similar relation along the rupture area of the largest instrumentally recorded Valdivia 1960 M w 9.5 megathrust earthquake. For the case of the Maule event, published differential multibeam bathymetric data confirms that coseismic slip must have propagated up to ∼6 km landwards of the deformation front and hence practically the entire base of the middle prism. Sediment dewatering and compaction processes might explain the competent rheology of the middle prism allowing shallow earthquake rupture. In contrast, the outer frontal prism made of poorly consolidated sediment has impeded the rupture up to the deformation front as high resolution seismic reflection and multibeam bathymetric data have not showed evidence for new deformation in the trench region. [ABSTRACT FROM AUTHOR]

The 15-story Alto Rio building built in 2006 in the city of Concepción, Chile, was the only modern building that collapsed catastrophically during the February 27, 2010 Mw 8.8 Maule earthquake, resulting in eight human casualties. This building was typical of many medium rise reinforced concrete bearing wall buildings designed and built in Chile during the period 1996-2009. Understanding the mechanism that led to the collapse of the Alto Rio building is of high relevance in the earthquake engineering community. For this purpose, a detailed three-dimensional nonlinear model of the as-built Alto Rio building structure was developed in the OpenSees analysis framework using the beam-truss modeling approach. The geometry of the structure was obtained directly from the architectural blueprints. Realistic cyclic material constitutive models were used for the reinforcing steel and concrete materials. This paper describes in detail the development of the building model. Furthermore, it presents the results obtained from a nonlinear pushover analysis and from a nonlinear time-history analysis using a bi-axial horizontal input ground motion generated by blending time-history ground accelerations recorded at an accelerograph station located 1.2 km from the building and time-history ground displacements recorded at a GPS station located 3.7 km from the building. [ABSTRACT FROM AUTHOR]

In this paper, nonlinear finite element model updating (FEMU) is performed to study the prediction accuracy of a state-of-the-art finite element (FE) model of a seismic isolated bridge (SIB). The seismic isolator model parameters are updated in two phases: using component-wise and system-wise FEMU. The isolator model parameter values estimated from 23 isolator component tests show a large scatter, and a poor goodness-of-fit (GOF) of the bridge response to the 2010 Maule Earthquake is obtained when most of those parameter sets are used for the isolator elements of the bridge FE model. In contrast, good agreement between the FE predicted and measured bridge response is obtained when the isolator model parameters are calibrated using the bridge response data recorded during the 2010 Mw 8.8 Maule, Chile Earthquake. The updated FE model is then used to reconstruct response quantities not recorded to gain more insight into the effects of seismic isolation during a strong earthquake. [ABSTRACT FROM AUTHOR]

Frame systems are the preferred structural systems in most seismic regions, where they are sometimes also combined with braces or walls. On the other hand Chile, one of the most seismically active countries in the world, is an exception to this practice. Any Chilean residential building higher than 5 stories is almost completely made up of reinforced concrete shear walls. Surprisingly, only 2% of the residential building inventory subjected to the 2010 Chile earthquake (M w 8.8) suffered severe damage, even though many structures were affected by ground accelerations larger than those prescribed in the Chilean seismic design code. This observation suggests that there is a large (and unintended) overstrength in this type of buildings. In a previous study, the authors showed that some of the traditional sources of overstrength mentioned in the literature could explain the lack of damage in low rise buildings but not in taller structures. Motivated by this observation, representative tall buildings were reanalyzed using more realistic models (e.g., flexural capacity of the walls assessed by fiber models) in order to get more insight into their actual seismic capacity. Two actual buildings of 17 and 26 stories that survived with no damage the 2010 Chile earthquake were analyzed by response history analysis. Results show that consideration of wall flanges (usually omitted in practice) cannot explain the lack of damage. On the other hand, it is observed that good performance might be a consequence of possible foundation uplift. Finally, the analyses also suggest that, even when there is no damage, elastic analysis has limitations to reproduce the actual observed behavior. [ABSTRACT FROM AUTHOR]

There is a long-standing debate whether or not the 2010 M 8.8 Maule earthquake filled a pre-existing seismic gap in which no large earthquake occurred for about 200 yr. Utilizing the inversion approach of Wang et al. that considers elastic strain accumulation and strain release during the earthquake cycle and includes the fault-coupling state as prior information in coseismic slip modelling, we investigate the inter- and coseismic slip balance for the 2010 M 8.8 Maule earthquake. The coseismic slip model is obtained as the product of three components: the interseismic backslip rate, the strain accumulation time, and the fraction of coseismically released slip potency (the product of slip and slip area) that may either fully or partially release the local strain. We construct slip models using the Slab1.0 fault geometry, and constrain the strain accumulation time for the 2010 Maule earthquake based on historical large earthquakes in the region. The results demonstrate that two slip clusters (north and south of the hypocentre) are required to model the geodetically measured coseismic displacements. The slip patch south of the hypocentre is located in a strongly coupled zone, and possibly released the local strain completely. The slip area north of the hypocentre overlaps with the interseismically creeping zone in which strain buildup may be low. The northern slip patch released higher slip potency than accumulated since the last mega-event in 1751, suggesting a possible dynamic overshoot during coseismic rupture (under the assumption that the last major earthquake has reset the regional strain). Alternatively, the last big event may not have fully released the strain in this region. Our study reveals that the Maule earthquake, combing its coseismic and post-seismic slip over 1.3 yr, released ~67-72 per cent of the local strain. Remaining strain is concentrated mainly south of the hypocentre, with potency equivalent to an M 8.4 event considering strain accumulation for 259 yr (since 1751). [ABSTRACT FROM AUTHOR]

Using Coulomb wedge solutions, we show that the effective strength of megathrusts ( μ b ′ ) can be determined from the geometry of out-of-sequence thrusts cutting through an accretionary or orogenic wedge. The method is first tested on central Chilean margin for which it yields a frictional strength of μ b ′ = 0.053 ( + 0.043 / − 0.024 ). The inferred value agrees well with previous strength estimates and with the tectonic response of the central Chilean wedge to 2010 M w 8.8 Maule earthquake. We then use the approach to constrain the strength of the collision megathrust of the central European Alps ∼30–20 million years ago. We find that the collision megathrust had a strength of μ b ′ = 0.065 ( + 0.035 / − 0.026 ), which is similarly low than the strength of subduction megathrusts. The result is integrated into a static force balance model to examine potential implications of a weak megathrust for the Alpine orogeny. The model results suggest that the Alpine megathrust supported a mean maximum elevation of ∼2,000 m and that growth of the wedge up to this elevation supported a switch from contractional to extensional tectonics in the interior of the Alps around 20 Ma. Finally, using the example of the Himalayas, we show how the strength of megathrusts may be also derived from the geometry of crustal ramps, which provides a valuable alternative if details on out-of-sequence thrusts are missing. [ABSTRACT FROM AUTHOR]

We developed a flexible planning tool by means of an optimization approach that is able to locate and assign refuge centers through facilitating buildings to provide shelter and medical and psychological assistance to the victims taking into account the quality of service. The article proposes variants within the optimization model that allow the decision maker to evaluate different realities in the plan. The performance of the models inside the red zone of the 2010 earthquake in Chile is illustrated. [ABSTRACT FROM AUTHOR]

In March 2010, a massive outbreak of gastroenteritis started in the region of Antofagasta (northern Chile). The outbreak was mainly attributed to Norovirus genogroup II although ETEC strains were also isolated with high frequency from clinical samples. We review this outbreak and determined that ETEC was an underestimated etiologic agent. [ABSTRACT FROM AUTHOR]

In this study, an inversion method is used to constrain the fault parameters of the 2010 Chile Earthquake using gravimetric observations. The formulation consists of using monthly Geopotential coefficients of GRACE observations in a conjunction with the analytical model of Okubo 1992 which accounts for the gravity changes resulting from Earthquake. At first, it is necessary to eliminate the hydrological and oceanic effects from GRACE monthly coefficients and then a spatio-spectral localization analysis, based on wavelet local analysis, should be used to filter the GRACE observations and to better refine the tectonic signal. Finally, the corrected GRACE observations are compared with the analytical model using a nonlinear inversion algorithm. Our results show discernible differences between the computed average slip using gravity observations and those predicted from other co-seismic models. In this study, fault parameters such as length, width, depth, dip, strike and slip are computed using the changes in gravity and gravity gradient components. By using the variations of gravity gradient components the above mentioned parameters are determined as 428 ± 6 Km, 203 ± 5 Km, 5 Km, 10°, 13° and 8 ± 1.2 m respectively. Moreover, the values of the seismic moment and moment magnitude are 2. 09 × 10 22 N m and 8.88 M w respectively which show the small differences with the values reported from USGS (1. 8 × 10 22 N m and 8.83 M w ). [ABSTRACT FROM AUTHOR]

An 8.8-magnitude earthquake occurred off the coast of Chile on 27 February 2010, displacing nearly 2,000 children aged less than five years to emergency housing camps. Nine months later, this study assessed the needs of 140 displaced 0-5-year-old children in six domains: caregiver stability and protection; health; housing; nutrition; psychosocial situation; and stimulation. Multivariate regression was applied to examine the degree to which emotional, physical, and social needs were associated with baseline characteristics and exposure to the earthquake, to stressful events, and to ongoing risks in the proximal post-earthquake context. In each domain, 20 per cent or fewer children had unmet needs. Of all children in the sample, 20 per cent had unmet needs in multiple domains. Children's emotional, physical, and social needs were associated with ongoing exposures amenable to intervention, more than with baseline characteristics or epicentre proximity. Relief efforts should address multiple interrelated domains of child well-being and ongoing risks in post-disaster settings. [ABSTRACT FROM AUTHOR]

This study used the rupture directivity theory to derive the fault parameters of the 2010 Mw 8.8 Chile earthquake on the basis of the azimuth-dependent source duration obtained from the Rayleigh-wave phase velocity. Results revealed that the 2010 Chile earthquake featured asymmetric bilateral faulting. The two rupture directions were N171°E (northward) and N17°E (southward), with rupture lengths of approximately 313 and 118 km, respectively, and were related to the locking degree in the source region. The entire source duration was approximately 187 s. After excluding the rise time from the source duration, the northward rupture velocity was approximately 2.02 km/s, faster than the southward rupture velocity (1.74 km/s). On average, the rupture velocity derived from this study was slower than that estimated from finite-fault inversion; however, several historical earthquakes in the Chile region also showed slow rupture velocity when using low-frequency signals, as surface waves do. Two earlier studies through global-positioning-system data analysis showed that the static stress drop of 50-70 bars for the 2010 Chile earthquake was higher than that for subduction-zone earthquakes. Hence, a remarkable feature was that the 2010 Chile earthquake had a slow rupture velocity and a high static stress drop, which suggested an inverse relationship between rupture velocity and static stress drop. [ABSTRACT FROM AUTHOR]

We test the static Coulomb stress triggering hypothesis for three recent megathrust earthquakes (the 2004 Sumatra-Andaman earthquake, the 2010 Maule earthquake, and the 2011 Tohoku-Oki earthquake) using focal mechanism solutions for actual earthquakes as receiver faults to calculate Coulomb stress changes. For the 2004 Sumatra-Andaman and 2011 Tohoku-Oki earthquakes, the median values of the Coulomb stress changes for 100 consecutive earthquakes revealed temporal changes from approximately zero before the megathrust earthquake to significant positive values following the mainshock, followed by decay over time. Furthermore, the ratio of the number of positively to negatively stressed receiver faults increased after the megathrust. These results support the triggering hypothesis that the static stress changes imparted by megathrust earthquakes cause seismicity changes. This is in contrast to the results of a previous study that used optimally orientated receiver faults to calculate Coulomb stress changes, and this difference indicates the importance of considering the spatial and temporal heterogeneities of receiver fault distributions. For the 2010 Maule earthquake, however, the results are strongly dependent on fault-slip models. Since most receiver faults are concentrated in the mainshock source region, slip models significantly affect the computed Coulomb stress changes and sometimes cause anomalous stress concentrations along the edge of each sub-fault. [ABSTRACT FROM AUTHOR]

The possibility of identifying the fault plane in the case when the source of an earthquake is described in the second-moment-based approximation is analyzed. The commonly occurring type of the earthquake source whose major axis and rupture propagation are directed along the strike axis is analyzed in detail. The possibility of identifying the fault plane of this source depending on the focal mechanisms of the earthquake is explored. The inferred conclusions are verified by the results obtained for two strong earthquakes: the Chilean earthquake that occurred in Maule on February 27, 2010 and the Sumatra offshore earthquake of April 11, 2012. [ABSTRACT FROM AUTHOR]

This article presents an overview of the different processes of data recollection and the analysis that took place during and after the emergency caused by the M 8.8 2010 Maule earthquake in central-south Chile. The article is not an exhaustive recollection of all of the processes and methodologies used; it rather points out some of the critical processes that took place with special emphasis in the earthquake characterization and building data. Although there are strong similarities in all of the different data recollection processes after the earthquake, the evidence shows that a rather disaggregate approach was used by the different stakeholders. Moreover, no common standards were implemented or used, and the resulting granularity and accuracy of the data was not comparable even for similar structures, which sometimes led to inadequate decisions. More centralized efforts were observed in resolving the emergency situations and getting the country back to normal operation, but the reconstruction process took different independent routes depending on several external factors and attitudes of individuals and communities. Several conclusions are presented that are lessons derived from this experience in dealing with a large amount of earthquake data. The most important being the true and immediate necessity of making all critical earthquake information available to anyone who seeks to study such data for a better understanding of the earthquake and its consequences. By looking at the information provided by all these data, we aim to finally improve seismic codes and engineering practice, which are important social goods. [ABSTRACT FROM AUTHOR]

Moderate to large earthquakes can increase the amount of water feeding stream flows, mobilizing excess water from deep groundwater, shallow groundwater, or the vadose zone. Here we examine the regional pattern of streamflow response to the Maule M8.8 earthquake across Chile's diverse topographic and hydro-climatic gradients. We combine streamflow analyses with groundwater flow modeling and a random forest classifier, and find that, after the earthquake, at least 85 streams had a change in flow. Discharge mostly increased ( n = 78 ) shortly after the earthquake, liberating an excess water volume of >1.1 km 3 , which is the largest ever reported following an earthquake. Several catchments had increased discharge of >50 mm, locally exceeding seasonal streamflow discharge under undisturbed conditions. Our modeling results favor enhanced vertical permeability induced by dynamic strain as the most probable process explaining the observed changes at the regional scale. Supporting this interpretation, our random forest classification identifies peak ground velocity and elevation extremes as most important for predicting streamflow response. Given the mean recurrence interval of ∼25 yr for >M8.0 earthquakes along the Peru–Chile Trench, our observations highlight the role of earthquakes in the regional water cycle, especially in arid environments. [ABSTRACT FROM AUTHOR]

Little is known about how the experience of an earthquake affects young children's cognitive outcomes. On February 27, 2010, a severe earthquake shook southern Chile. The earthquake occurred during the course of a large-scale evaluation of an early childhood education intervention (child average age = 53 months) in Santiago, such that one cohort of children (n = 698) experienced baseline data collection 3-12 weeks after the earthquake occurred, while a different cohort of children (n = 720) did not. In this paper, we used these available evaluation data to conduct two sets of analyses that explore the relationship between preschool children's exposure to the 2010 Chilean earthquake and their early language, pre-literacy, mathematics and executive function outcomes. In the first set of analyses, we employed a propensity score analysis to estimate the short-term effect of the earthquake on preschool-aged children's early learning and executive function outcomes. Results suggest that children who experienced the earthquake had lower scores on some early language and pre-literacy assessments than those who did not, with effect sizes of approximately 20% of a standard deviation. Results from the second set of analyses suggest that among the families who experienced the earthquake, children whose parents reported more earthquake-related stressors performed significantly lower on some early language and pre-literacy outcomes. Implications of these findings for disaster relief efforts and future research are discussed. [ABSTRACT FROM AUTHOR]

In this study the gravitational gradient changes caused by faulting on a finite rectangular plane buried in a homogenous half-space are computed using an analytical model which is a function of fault parameters. The sensitivity analysis of the analytical model with optional parameters revealed that the model is sensitive to the most of the fault parameters such as slip, depth, dip and is not sensitive to the strike. Also the results show that the model is sensitive to the length and the width of the fault. Moreover, the gravitation and gravitational gradient changes for the case of the Maule earthquake on 27 February 2010 are directly computed by GRACE observations without need to fault parameters information. Since the high-frequency contents in gravitational field variation can be amplified by deriving the gravitational gradients, the GRACE-derived coseismic gravitational gradient changes clearly delineate the fault lines and better define the extent of the coseismic deformation. [ABSTRACT FROM AUTHOR]

The present study examines the psychometric properties of the Posttraumatic Growth Inventory for Children in its brief version (PTGI-C-R; Kilmer et al., 2009), an inventory that measured positive personal changes that occur after experiencing a traumatic event. The PTGI-C-R was applied to 393 children from 10 to 15 years of age affected by the earthquake and tsunami in Chile February 27, 2010. The scale showed good internal consistency and discriminant validity in relation to an inventory of posttraumatic stress symptoms. It was also able to discriminate between children who had high exposure to the earthquake and children with mild or no exposure. Confirmatory factor analysis showed adequate goodness of fit for a 2-factor structure: general change and spiritual change. The PTGI-C-R also showed factorial invariance in groups of high and low exposure. These positive psychometric qualities indicate the utility of the instrument for use in children and adolescents exposed to natural disasters. (PsycINFO Database Record [ABSTRACT FROM AUTHOR]

Previous earthquakes, such as the 2010 Maule earthquake in Chile, have demonstrated the need to establish suitable predictors of compressive or tensile strains in concrete or steel in reinforced concrete shear walls, which can provide limit states or confinement requirements. Slender walls are commonly controlled by flexural deformations that can be divided into elastic and inelastic components. This study provides calibrated expressions for the elastic and inelastic components of flexural deformations using a fiber model for slender walls. These expressions are obtained for rectangular and T-shaped walls. The elastic component is dependent on the axial load and the boundary steel reinforcement ratio. The impact of wall coupling is investigated, which requires a correction for the elastic component. The investigation of the inelastic component is based on a plastic hinge model, in which the length of the plastic hinge is a function of the lateral inelastic drift of the wall among other parameters. The traditional linear inelastic curvature distribution over the wall height is also modified for cases with steel reinforcement with a long yield plateau or low strain hardening, which results in a larger curvature at the wall base. The distribution is validated with experimental data from the literature. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Reloca Slide is the relict of an ~24-km3 submarine slope collapse at the base of the convergent continental margin of central Chile. Bathymetric and seismic data show that directly to the north and south of the slide the lower continental slope is steep (~10°), the deformation front is shifted landwards by 10-15 km, and the frontal accretionary prism is uplifted. In contrast, ~80 km to the north the lower continental margin presents a lower slope angle of about 4° and a wide frontal accretionary prism. We propose that high effective basal friction conditions at the base of the accretionary prism favoured basal accretion of sediment and over-steepening of the continental slope, producing massive submarine mass wasting in the Reloca region. This area also spatially correlates with a zone of low coseismic slip of the 2010 Maule megathrust earthquake, which is consistent with high basal frictional coefficients. [ABSTRACT FROM AUTHOR]

Reinforced concrete shear wall buildings have shown, in statistical terms, an adequate performance in past seismic events. However, a specific damage pattern was observed in 2010 Chile earthquake in some shear walls located in the lower building stories, usually associated with high axial stresses, lack of transverse reinforcement, and vertical irregularity. Results show that the nature of this failure led to a sudden degradation in strength and stiffness of walls and resulted in very limited ductility. This research aims to study analytically this damage pattern of shear wall buildings during the 2010 earthquake. By starting with two-dimensional inelastic pushover finite element models using diana, two walls that were severely damaged during the earthquake were studied in detail using different load patterns and stress-strain constitutive relationships for concrete in compression. These models were validated with experimental data of four reinforced concrete walls available in the literature. It can be shown that the geometry of the damage in the building walls cannot be correctly represented by conventional pushover load patterns that ignore the lateral and axial interaction. Indeed, the failure mechanism of walls shows strong coupling between lateral and vertical deformations within the plane of the wall. Results shown for a three-dimensional inelastic analysis of the building are consistent with these two-dimensional results, and predict a brittle failure of the structure. However, these models predict a large increase in axial load in the walls, which needs to be validated further with more experimental and analytical studies. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]