Marine forearc structure of eastern Java and its role in the 1994 Java tsunami earthquake

We resolve a previously unrecognized shallow subducting seamount from a re-processed multichannel seismic profile crossing the 1994 Mw 7.8 Java tsunami earthquake rupture area. Seamount subduction occurs where the overriding plate experiences uplift by lateral shortening and vertical thickening. Pronounced back-thrusting at the landward slope of the forearc high and the formation of splay faults branching off the landward flank of the subducting seamount are observed. The location of the seamount in relation to the 1994 earthquake hypocentre and its co-seismic slip model suggests that the seamount acted as a seismic barrier to the up-dip co-seismic rupture propagation of this moderate-size earthquake.

Memory and the Dissolution of the Monasteries in Early Modern England

The dissolution of the monasteries was recalled by individuals and communities alike as a seismic rupture in the religious, cultural, and socio-economic fabric of early modern England. It was also profoundly important in shaping contemporary historical consciousness, the topographical imagination, and local tradition. Memory and the Dissolution is a book about the dissolution of the monasteries after the dissolution. Harriet Lyon argues that our understanding of this historical moment is enriched by taking a long chronological view of the suppression, by exploring how it was remembered to those who witnessed it and how this memory evolved in subsequent generations. Exposing and repudiating the assumptions of a conventional historiography that has long been coloured by Henrician narratives and sources, this book reveals that the fall of the religious houses was remembered as one of the most profound and controversial transformations of the entire English Reformation.

Marine forearc structure of eastern Java and its role in the 1994 Java tsunami earthquake

We resolve a previously unrecognized shallow subducting seamount from a re-processed multichannel seismic depth image crossing the 1994 M7.8 Java tsunami earthquake slip area. Seamount subduction is related to the uplift of the overriding plate by lateral shortening and vertical thickening, causing pronounced back-thrusting at the landward slope of the forearc high and the formation of splay faults branching off the landward flank of the subducting seamount. The location of the seamount in relation to the 1994 earthquake hypocentre and its co-seismic slip model suggests that the seamount acted as a seismic barrier to the up-dip co-seismic rupture propagation of this moderate size earthquake. The wrapping of the co-seismic slip contours around the seamount indicates that it diverted rupture propagation, documenting the control of forearc structures on seismic rupture.

Mirror fault formation and coseismic slip at surface conditions: an example of faulting in unconsolidated deposits in the Central Apennines (Italy)

<p>Faulting in seismically active regions commonly involves the deformation of unconsolidated to poorly lithified sediments at shallow to near-surface depths. When compared to classic crustal strength profiles that predict a velocity-strengthening behaviour for the first few km of depth, the propagation of seismic rupture to the surface appears counterintuitive. Rock deformation experiments have shown an inverse relationship between normal stress and displacement needed to the onset of dynamic weakening during seismic slip, meaning that for a seismic rupture to be able to propagate towards the surface, displacements should be large enough to counter the progressive decrease of normal and confining stresses.</p><p>In this contribution, we document the occurrence of mirror-like faults that formed within 20-30 m-thick, unconsolidated colluvium fan deposits at the hanging wall of the active Vado di Corno Fault Zone (VCFZ) in the Central Apennines, Italy. The deposits lie in direct contact with the master normal-fault surface, are Late Pleistocene to Holocene in age, and consist of angular carbonate clasts with grain size ranging ~0.1-10 mm derived from the dismantling of the adjacent VCFZ footwall. Field observations of cross cutting relationships and marker layer displacements suggest a maximum formation depth of the faults of c. 20-30 m and slip accommodated along single faults on the order of few cm. Faults are organised in three sets: subvertical, N-S and NE-SW trending faults, and WNW-ESE striking faults, synthetic and antithetic to the VCFZ master fault surface (N195/55°). Faults are commonly lineated with a dip-slip to slightly oblique kinematic.</p><p>Detailed microstructural analysis of the mirror faults shows extreme strain localization on a 2-5 µm thick principal slip zone composed of calcite nanograins ranging 10s-100s nm in size with amorphous material and phyllosilicates occurring along grain boundaries and within intragranular porosity. Locally, aggregates of nanograins coalesce and transition to µm-sized polygonal, larger grains. Calcite nanograins are mostly equant, with straight grain boundaries, 120° dihedral angles, and negligible porosity. These microstructures strongly resemble high temperature recrystallization structures documented along seismic faults exhumed from >5 km of depth, where stresses are significantly larger. In our case, field constraints show that deformation occurred in very confining stress conditions and with limited displacement.</p><p>Collectively, our observations provide new documentation on the conditions for the formation of mirror faults and new insights into the mechanics of faulting and strain accommodation in the shallowest part of the crust (< 1 km).</p>

Spatio-temporal evolution of afterslip following the Mw 7.8 Pedernales earthquake, Ecuador

<p>We use 40 continuous GPS stations in Ecuador to quantify 3 years of the  post-seismic deformation that followed the Mw 7.8 April 16 Pedernales earthquake. We perform a kinematic inversion solving for the daily slip along the subduction to retrieve the afterslip evolution through time and space.</p><p>Rolandone et al. (2018) had found that the afterslip during the first 30 days following the earthquake was abnormally large and rapid, mainly developing at discrete patches north and south updip of the co-seismic rupture. We find that large slip and slip rate continue at both location, decreasing through time. However, models suggest that modulations of slip rate occur within those areas, with episods of slip acceleration sometimes associated with the occurrence of moderate size aftershocks.  Aside these patches, afterslip developed updip the co-seismic rupture between the patches and downdip of the coseismic rupture, with little slip occurring within the co-seismic rupture.</p><p>The overall model confirms a model of a seismic asperity encompassed in a subduction interface releasing stress through aseismic processes. However, some areas experiencing afterslip appear to be locked before the earthquake. Furthermore, those areas experienced SSE before the earthquake and during the afterslip period, raising the question of the friction parameter controlling their behavior.</p><p>In terms of moment, the amount of afterslip after 3 years is equivalent to 90% of the moment released by the Pedernales earthquake. This observation highlights that aseismic slip has an important contribution to the balance of slip during the earthquake cycle along the central Ecuador segment. This observation strengthens the proposed hypothesis of earthquake an super-cycle in central Ecuador (Nocquet et al., 2017), by confirming that the occurrence of three successive major earthquakes within 110 years exceeds the moment accumulation as derived from a decade of interseismic coupling models spanning a decade before the 2016 earthquake.</p>

A transient in surface motions dominated by deep afterslip subsequent to a shallow supershear earthquake: the 2018 Mw 7.5 Palu case.

<div> <div> <div> <p>The 2018 <em>M<sub>w</sub></em> 7.5 Palu earthquake is a remarkable strike-slip event due to its nature as a shallow supershear fault rupture across several segments and a destructive tsunami that followed co-seismic deformation. GPS offsets in the wake of the 2018 earthquake display a transient in the surface motions of northwest Sulawesi. A Bayesian approach identifies (predominantly a-seismic) deep afterslip on and below the co-seismic rupture plane as the dominant physical mechanism causing the cumulative, post-seismic, surface displacements whereas viscous relaxation of the lower crust and poro-elastic rebound contribute negligibly. We confirm a correlation between shallow supershear rupture and post-seismic surface transients with afterslip activity in the zone below an inter-seismically locked fault plane where the slip rate tapers from zero to creeping.</p> </div> </div> </div>

The Trial against Disinformation

This chapter considers the trial and subsequent conviction of scientists following the April 2009 earthquake in the city of L'Aquila. It talks about members of the National Commission for the Forecast and Prevention of Major Risks (Commissione Grandi Rischi) that were charged with manslaughter and grievous injury for issuing public reassurances in 2012, which were alleged to frame the victims' choice to stay home and, subsequently, led to their deaths. It also shows how the L'Aquila trial represents a seismic rupture of belief, which became a judicial experiment in holding disinformation accountable. The chapter explores why citizens of L'Aquila have found scientists' public statements credible. It elaborates how the incrimination of Commissione Grandi Rischi meant that Italians had faith in the moral capabilities of politicians and the purity of scientific truth, suspending their more rational skepticism to the contrary.

Porosity of metamorphic rocks and fluid migration within subduction interfaces

<p><strong>            </strong>Large earthquakes break the subduction interface to depths of 60 to 80 km. Current models hold that seismic rupture occurs when fluid overpressure builds in link with porosity cycles, an assumption still to be experimentally validated at high pressures. Porosities of subduction zone rocks are experimentally determined under pressures equivalent to depths of up to 90 km with a novel experimental approach that uses Raman deuterium-hydrogen mapping. Natural rocks (blueschists, antigorite serpentinites, and chlorite-schists) representing a typical cross-section of the subduction interface corresponding to the deep seismogenic zone are investigated. In serpentinite, and to a smaller extent blueschist, porosity increases with deformation, whereas chlorite-rich schists remain impermeable regardless of their deformation history[ 1]. Such a contrasting behavior explains the observation of over-pressurized oceanic crust and the limited hydration of the forearc mantle wedge. These results provide quantitative evidence that serpentinite, and likely blueschist, may undergo porosity cycles making possible the downdip propagation of large seismic rupture to great depths. </p><p>[1] Ganzhorn, A.C., Pilorgé, H., Reynard, B., 2019, Earth and Planetary Science Letters, 522: 107-117.</p>