Role of Lower Crust in the Postseismic Deformation of the 2010 Maule Earthquake: Insights from a Model with Power-Law Rheology

2019 ◽  
Vol 176 (9) ◽  
pp. 3913-3928 ◽  
Author(s):  
Carlos Peña ◽  
Oliver Heidbach ◽  
Marcos Moreno ◽  
Jonathan Bedford ◽  
Moritz Ziegler ◽  
...  
Keyword(s):  
Power Law ◽  
Lower Crust ◽  
Postseismic Deformation ◽  
Maule Earthquake ◽  
2010 Maule Earthquake

scholarly journals Transient Deformation and Stress Patterns Induced by the 2010 Maule Earthquake in the Illapel Segment

2021 ◽  
Vol 9 ◽  
Author(s):  
Carlos Peña ◽  
Oliver Heidbach ◽  
Marcos Moreno ◽  
Daniel Melnick ◽  
Onno Oncken
Keyword(s):  
Power Law ◽  
Postseismic Deformation ◽  
Relaxation Processes ◽  
Megathrust Earthquakes ◽  
Transient Deformation ◽  
Maule Earthquake ◽  
2010 Maule Earthquake ◽  
Illapel Earthquake ◽  
The Impact ◽  
Rheology Model

Evaluating the transfer of stresses from megathrust earthquakes to adjacent segments is fundamental to assess seismic hazard. Here, we use a 3D forward model as well as GPS and seismic data to investigate the transient deformation and Coulomb Failure Stresses (CFS) changes induced by the 2010 Maule earthquake in its northern segment, where the Mw 8.3 Illapel earthquake occurred in 2015. The 3D model incorporates the coseismically instantaneous, elastic response, and time-dependent afterslip and viscoelastic relaxation processes in the postseismic period. We particularly examine the impact of linear and power-law rheology on the resulting postseismic deformation and CFS changes that may have triggered the Illapel earthquake. At the Illapel hypocenter, our model results in CFS changes of ∼0.06 bar due to the coseismic and postseismic deformation, where the coseismic deformation accounts for ∼85% of the total CFS changes. This is below the assumed triggering threshold of 0.1 bar and, compared to the annual loading rate of the plate interface, represents a clock advance of approximately only 2 months. However, we find that sixteen events with Mw ≥ 5 in the southern region occurred in regions of CFS changes > 0.1 bar, indicating a potential triggering by the Maule event. Interestingly, while the power-law rheology model increases the positive coseismic CFS changes, the linear rheology reduces them. This is due to the opposite polarity of the postseismic displacements resulting from the rheology model choice. The power-law rheology model generates surface displacements that fit better to the GPS-observed landward displacement pattern.

Assessing disaster capitalism in post-disaster processes in Chile: neoliberal reforms and the role of the corporate class

2020 ◽  
Vol 29 (6) ◽  
pp. 831-847
Author(s):  
Vicente Sandoval ◽  
Claudia Gonzalez-Muzzio ◽  
Carlos Villalobos ◽  
Juan Pablo Sarmiento ◽  
Gabriela Hoberman
Keyword(s):  
Private Sector ◽  
Private Funding ◽  
Content Type ◽  
Neoliberal Reforms ◽  
Maule Earthquake ◽  
Disaster Capitalism ◽  
2010 Maule Earthquake ◽  
Cross Case Analysis ◽  
Post Disaster

PurposeThis paper examines disaster capitalism in Chile, that is, the relationships between disasters and neoliberalism. It looks at two post-disaster dimensions: disasters as windows of opportunity to introduce political reforms and disasters as occasions for the corporate class to capitalize on such disasters.Design/methodology/approachTwo indices, disaster capitalism (DC) and post-disaster private involvement (PDPI), are proposed for cross-case analysis. They are based on legal records, institutional reports and economic data. The DC assesses the introduction of reforms following disasters, while PDPI evaluates the share of public-private funding used for recovery. Both indices are applied here to two disasters in Chile: the 2010 Maule earthquake, and the 2008 Chaitén volcanic eruption.FindingsResults show that the highly neoliberal Chilean context leaves limited space for new neoliberal reforms. Although recovery is implemented predominantly through the private sector, the state still assumes greater responsibility for recovery costs. Results also detect poor levels of participation from the private sector in accounting their efforts and making them publicly available. Likewise, the research suggests that neoliberal reforms become more likely after disasters. However, the preexisting politico-economic context matters. Finally, there is clearly a need for data systematization in post-disaster recovery.Originality/valueIn the Chilean context, the indices proved beneficial as a strategy for data collection and a method for scrutinizing the implications of neoliberal policy implemented in the wake of disasters, as well as in evaluating the role of the corporate class during recovery.

Constraints on the rheology of the mid- to lower continental crust from geodetic studies of the earthquake deformation cycle

2020 ◽  
Author(s):  
Tim Wright ◽  
Tom Ingleby ◽  
Ekbal Hussain
Keyword(s):  
Shear Zone ◽  
Continental Crust ◽  
Power Law ◽  
Lower Crust ◽  
Postseismic Deformation ◽  
Strain Accumulation ◽  
Earthquake Cycle ◽  
Accumulation Rates ◽  
Deformation Cycle ◽  
Time Invariant

<p>In this presentation I will review geodetic constraints on the rheology of the mid- to lower continental crust from observations and models of all phases of the earthquake deformation cycle. I will focus on observations of slow interseismic strain accumulation and rapid postseismic strain transients, both of which result primarily from deformation in the mid- to lower crust. I will argue that, with a few exceptions, interseismic strain is focused in zones around faults with widths that are compatible with strain at depth being focused on a fault or distributed in a shear zone up to ~3 x the seismogenic layer thickness. I will show that for the North Anatolian Fault, the strain accumulation rate appears to be approximately constant for the entire earthquake cycle, once the postseismic transient has decayed. This is consistent with observations at other fault where geodetic measurements were made prior to major earthquakes; the broad agreement between geological and geodetic estimates of slip rate is also consistent with interseismic strain accumulation rates being relatively time invariant. Time-invariant interseismic strain accumulation rates require a relatively strong mid- to lower crust, where relaxation times are equal to or greater than the average earthquake revisit time. Postseismic deformation transients are commonly observed following most earthquakes, but they are interpreted using a variety of very different deformation mechanisms. By compiling all observations of postseismic deformation we show that the largest transient postseismic velocities decay following a simple t<sup>-1</sup> power-law, analogous to Omori’s law for aftershock decay. This is consistent with frictional afterslip and/or power-law creep in a narrow shear zone. This model of a weak shear zone embedded within a stronger substrate can explain most observations of the earthquake deformation cycle. Exceptions to this simple model might occur in locations where the lower crust is weaker, perhaps due to the presence of partial melt. Geological constraints on rheology are critical for making further progress in understanding the earthquake deformation cycle – geological models for the mid- to lower crust can be tested by comparing geodetic observations with geologically-realistic earthquake cycle models.</p>

Evolution of seismic design codes of highway bridges in Chile

2021 ◽  
pp. 875529302098801
Author(s):  
José Wilches ◽  
Hernán Santa Maria ◽  
Roberto Leon ◽  
Rafael Riddell ◽  
Matías Hube ◽  
...  
Keyword(s):  
Seismic Design ◽  
Failure Modes ◽  
Highway Bridges ◽  
Design Codes ◽  
Seismic Codes ◽  
Analysis And Design ◽  
Residual Displacements ◽  
Shear Keys ◽  
Maule Earthquake ◽  
2010 Maule Earthquake

Chile, as a country with a long history of strong seismicity, has a record of both a constant upgrading of its seismic design codes and structural systems, particularly for bridges, as a result of major earthquakes. Recent earthquakes in Chile have produced extensive damage to highway bridges, such as deck collapses, large transverse residual displacements, yielding and failure of shear keys, and unseating of the main girders, demonstrating that bridges are highly vulnerable structures. Much of this damage can be attributed to construction problems and poor detailing guidelines in design codes. After the 2010 Maule earthquake, new structural design criteria were incorporated for the seismic design of bridges in Chile. The most significant change was that a site coefficient was included for the estimation of the seismic design forces in the shear keys, seismic bars, and diaphragms. This article first traces the historical development of earthquakes and construction systems in Chile to provide a context for the evolution of Chilean seismic codes. It then describes the seismic performance of highway bridges during the 2010 Maule earthquake, including the description of the main failure modes observed in bridges. Finally, this article provides a comparison of the Chilean bridge seismic code against the Japanese and United States codes, considering that these codes have a great influence on the seismic codes for Chilean bridges. The article demonstrates that bridge design and construction practices in Chile have evolved substantially in their requirements for the analysis and design of structural elements, such as in the definition of the seismic hazard to be considered, tending toward more conservative approaches in an effort to improve structural performance and reliability for Chilean bridges.

scholarly journals The Role of Lower Crustal Rheology in Lithospheric Delamination During Orogeny

2021 ◽  
Vol 9 ◽  
Author(s):  
Lin Chen
Keyword(s):  
Lower Crust ◽  
Numerical Models ◽  
The Tibetan Plateau ◽  
Mantle Lithosphere ◽  
Laboratory Studies ◽  
Surface Uplift ◽  
Continental Lower Crust ◽  
Lower Crustal ◽  
Flow Laws

The continental lower crust is an important composition- and strength-jump layer in the lithosphere. Laboratory studies show its strength varies greatly due to a wide variety of composition. How the lower crust rheology influences the collisional orogeny remains poorly understood. Here I investigate the role of the lower crust rheology in the evolution of an orogen subject to horizontal shortening using 2D numerical models. A range of lower crustal flow laws from laboratory studies are tested to examine their effects on the styles of the accommodation of convergence. Three distinct styles are observed: 1) downwelling and subsequent delamination of orogen lithosphere mantle as a coherent slab; 2) localized thickening of orogen lithosphere; and 3) underthrusting of peripheral strong lithospheres below the orogen. Delamination occurs only if the orogen lower crust rheology is represented by the weak end-member of flow laws. The delamination is followed by partial melting of the lower crust and punctuated surface uplift confined to the orogen central region. For a moderately or extremely strong orogen lower crust, topography highs only develop on both sides of the orogen. In the Tibetan plateau, the crust has been doubly thickened but the underlying mantle lithosphere is highly heterogeneous. I suggest that the subvertical high-velocity mantle structures, as observed in southern and western Tibet, may exemplify localized delamination of the mantle lithosphere due to rheological weakening of the Tibetan lower crust.

scholarly journals Illuminating subduction zone rheological properties in the wake of a giant earthquake

2019 ◽  
Vol 5 (12) ◽  
pp. eaax6720 ◽  
Author(s):  
Jonathan R. Weiss ◽  
Qiang Qiu ◽  
Sylvain Barbot ◽  
Tim J. Wright ◽  
James H. Foster ◽  
...  
Keyword(s):  
Subduction Zone ◽  
Subduction Zones ◽  
Three Dimensional ◽  
Surface Strain ◽  
Postseismic Deformation ◽  
Crust And Upper Mantle ◽  
Plate Convergence ◽  
Maule Earthquake ◽  
History Of ◽  
Dependent Viscosity

Deformation associated with plate convergence at subduction zones is accommodated by a complex system involving fault slip and viscoelastic flow. These processes have proven difficult to disentangle. The 2010 Mw 8.8 Maule earthquake occurred close to the Chilean coast within a dense network of continuously recording Global Positioning System stations, which provide a comprehensive history of surface strain. We use these data to assemble a detailed picture of a structurally controlled megathrust fault frictional patchwork and the three-dimensional rheological and time-dependent viscosity structure of the lower crust and upper mantle, all of which control the relative importance of afterslip and viscoelastic relaxation during postseismic deformation. These results enhance our understanding of subduction dynamics including the interplay of localized and distributed deformation during the subduction zone earthquake cycle.

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