Can coseismic static stress changes sustain postseismic degassing?

Earthquakes can trigger increased degassing in hydrogeological systems. Many of these systems return to preseismic conditions after months, but sometimes postseismic degassing lasts for years. The factors controlling such long-lasting degassing are poorly known. I explored the potential role of diverse triggering mechanisms (i.e., dynamic and static stress changes, volumetric strain) for three large earthquakes that induced postseismic degassing (the Wenchuan [China], Maule [Chile], and Gorkha [Nepal] earthquakes). The lessons from this study suggest that hydrogeological systems can respond to earthquakes in various ways, and different causal mechanisms can play a role. Persistent increased CO2 flux from hot springs has been documented after the Gorkha earthquake. These hot springs had their feeder systems dominantly unclamped, suggesting that sufficiently large normal stress changes may sustain late postseismic degassing. The results of this study are twofold: (1) they show a spatial correlation between unclamping stress and increased gas flow, and (2) they provide an explanation for protracted increased degassing.

Anti-phospholipase A2 receptor in Non-lupus Patients with Membranous Nephropathy and Crescents

Introduction: Anti-phospholipase A2 receptor (PLA2R) is detected in approximately 70% of biopsies of “primary” membranous nephropathy (MN). Crescents in MN in non-lupus patients suggest additional injury, such as antineutrophil cytoplasmic antibody (ANCA) or anti-glomerular basement membrane (anti-GBM)-associated glomerulonephritis and is postulated to reflect injury by a mechanism that unmasks cryptic epitopes leading to the second autoantibody. Methods: We studied PLA2R staining in non-lupus patients with MN and crescents. Native renal biopsies in 16 non-lupus patients with MN and crescents were stained for PLA2R. Results: The patients included 5 women and 11 men, with mean age 61 yrs and elevated serum creatinine (mean 4.68 mg/dL). Hematuria and proteinuria (mean 4.97 g/d) were documented in 13 patients. Two patients had positive serum anti-GBM antibody. Nine of eleven patients tested for ANCA were positive, with p-ANCA (n=4), c-ANCA (n=2), or both (n=1), with two not specified. On average, 27% of glomeruli had crescents. One patient had an initial biopsy with MN, 4 years later had MN with crescent, and 7 years later had rebiopsy with persistent MN with crescents. One patient had ANCA-associated vasculitis, and 5 years later had MN and crescent. The remaining 14 patients had concurrent diagnoses of MN and crescents. PLA2R was positive in 5 cases, 3 with ANCA positivity, 2 with unknown ANCA status, and none with anti-GBM disease. The patient with initial MN preceding crescent was PLA2R positive; the patient with initial ANCA-associated vasculitis preceding MN was PLA2R negative. Conclusions: Most patients (64%) presented with concomitant MN and crescents, with rare occurrence of an initial disease process followed later by the second injury. PLA2R was positive in 31% of patients, suggesting most are secondary MN. Further study to determine the cryptic epitopes may shed light on the triggering mechanisms for these rare but unlikely coincidental glomerular injuries.

Magnitude and Timing of the Tiltill Rockslide in Yosemite National Park, California

ABSTRACT Yosemite National Park, California, is one of the best-documented sites of historical rockfalls and other rock slope failures; however, past work shows that this record does not capture the infrequent largest occurrences, prehistoric events orders of magnitude larger than the largest historic ones. These large prehistoric events are evident as voluminous bouldery landslide deposits, permitting volume and age quantification to better understand local volume–frequency relationships, potential triggering mechanisms, and the hazard such events might pose. The Tiltill rockslide in northern Yosemite is one such example, consisting of 2.1 × 106 m3 ± 1.6 × 106 m3 of talus (1.5 × 106 m3 original volume of rock mass) that slid across the floor of Tiltill Valley, partially damming Tiltill Creek to create a seasonal pond that drains through and around the rockslide mass. This volume and the rockslide's effective coefficient of friction, 0.47, place it near the boundary between long-runout landslides and ordinary Coulomb failure. Although the rockslide superficially appears to consist of two separate lobes, statistically indistinguishable 10Be exposure dates from eight samples indicate a single event that occurred at 13.0 ± 0.8 ka. The age of the Tiltill rockslide and its relatively low elevation compared to equilibrium line altitudes at this place and time make glacial debutressing a highly unlikely triggering mechanism. Seismic shaking associated with fault rupture along the eastern Sierra Nevada is shown to be a plausible but unverified trigger.

Thermo-barometric constraints on the Mt. Etna 2015 eruptive event

The petrological study of volcanic products emitted during the paroxysmal events of December 2015 from the summit craters of Mount Etna allow us to constrain T-P-XH2O phase stability, crystallization conditions, and mixing processes along the main open-conduit feeding system. In this study, we discuss new geochemical, thermo-barometric data and related Rhyolite-MELTS modelling of the eruptive activity that involved the concomitant activation of all summit craters. The results, in comparison with the previous paroxysmal events of the 2011–2012, reinforce the model of a vertically extended feeding system and highlight that the activity at the New South-East Crater was fed by magma residing at a significantly shallower depth with respect to the Central Craters (CC) and North-East Crater (NEC), even if all conduits were fed by a common deep (P = 530–440 MPa) basic magmatic input. Plagioclase dissolution, resorption textures, and the Rhyolite-MELTS stability model corroborate its dependence on H2O content; thus, suggesting that further studies on the effect that flushing from fluids with different H2O/CO2 ratio are needed to understand the eruption-triggering mechanisms for high energetic strombolian paroxysmal episodes.

Evaluation of failure of slopes with shaking-induced cracks in response to rainfall

Centrifuge model tests on slopes subject to shaking and rainfall have been performed to examine the response of slopes with shaking-induced cracks to subsequent rainfall and evaluate the corresponding landslide-triggering mechanisms. The failure pattern of the slope subject to shaking and then rainfall was found different from that of the slope subject to only rainfall. When shaking caused cracks on the slope shoulder and rupture line below, the mobilized soil slid along the slip surface that extended to the rupture line, the main crack became the crown of the undisturbed ground once the slope was subject to a subsequent rain event, and the progression of the landslide was related to the rainfall intensity. During the landslide caused by light rainfall, the main scarp kept exposing itself in the vertically downward direction while the ground behind the main crack in the crack-containing slope remained undisturbed. The detrimental effect of cracks on soil displacement was more evident when the slope was exposed to heavy post-shaking rainfall, resulting in a rapid and massive landslide. Additionally, the volume of displaced material of the landslide, the main scarp area on the upper edge, and the zone of accumulation were larger in the crack-containing slope subject to heavy rainfall, in comparison with those in the crack-free slope. The deformation pattern of slopes with shaking-induced cracks during rainfall was closely related to rainfall intensity and the factor of safety provided a preliminary estimation of slope stability during rainfall. Moreover, even when subjected to the same rainfall, the slopes with antecedent shaking-induced cracks displayed different levels of deformation. The slope that experienced larger shaking had greater deformation under the following rainfall, and the shaking-induced slope deformation also controlled the slip surface location. Finally, the velocity of rainfall-induced landslide could be greatly influenced by the prior shaking event alone. Despite being under light rainfall, the slope that has encountered intense previous shaking exhibited an instant landslide.

Triggering Mechanisms of Gayari Avalanche, Pakistan

A massive snow avalanche occurred on April, 2012 at Gayari, located in NE part of Pakistan, close to India and China Border. The catastrophic avalanche killed nearly 148 people, majority of which were Pakistan army personnel destroying army base camp. To mitigate its future hazard, different triggering mechanisms have been investigated in this study. We contemplate that the avalanche was triggered due to snow pack existence on favorable slope in combination with different meteorological conditions and anomalous ground vibration. The avalanche occurrence clock was advanced by two earthquakes: M4.1 at a distance ∼ 125 km that occurred about 21 hours before and another comparatively larger (M5.6) earthquake that occurred comparatively at larger distance (∼ 370 km) and longer time (∼ 25 days) before which have significantly changed the loading conditions. The latter event (M 5.6) has imparted maximum peak dynamic stress and cumulative seismic moment a month before the avalanche. Interestingly the avalanche occurred within the seismic coda of M2.8 earthquake from Hindu Kush region, located at 560 km distance. Although the size and its expected impact on avalanche might be minor but its role in instantaneous triggering cannot be ruled out. Even smaller events at larger distance have been reported to cause snow avalanches in same environments. The presence of cracks within the avalanche, were further weaken by persistence of extremely low temperature (lowest in the past decade), causing high precipitation rate along with altering the mechanical properties of the weak layer within the snow pack. Robust wind pressure pattern highest and lowest in March and April, 2012 respectively might be responsible for abrupt changes in loading conditions.

Dendrimer end-terminal motif-dependent evasion of human complement and complement activation through IgM hitchhiking

Complement is an enzymatic humoral pattern-recognition defence system of the body. Non-specific deposition of blood biomolecules on nanomedicines triggers complement activation through the alternative pathway, but complement-triggering mechanisms of nanomaterials with dimensions comparable to or smaller than many globular blood proteins are unknown. Here we study this using a library of <6 nm poly(amido amine) dendrimers bearing different end-terminal functional groups. Dendrimers are not sensed by C1q and mannan-binding lectin, and hence do not trigger complement activation through these pattern-recognition molecules. While, pyrrolidone- and carboxylic acid-terminated dendrimers fully evade complement response, and independent of factor H modulation, binding of amine-terminated dendrimers to a subset of natural IgM glycoforms triggers complement activation through lectin pathway-IgM axis. These findings contribute to mechanistic understanding of complement surveillance of dendrimeric materials, and provide opportunities for dendrimer-driven engineering of complement-safe nanomedicines and medical devices.