The Ocean's Impact on Slow Slip Events Gomberg, J.; Baxter, P.; Smith, E. ...
Geophysical research letters,
28 July 2020, Letnik:
47, Številka:
14
Journal Article
Recenzirano
We test the hypothesis that ocean seafloor pressures impart stresses that alter the initiation or termination of transient slow slip events (SSEs) on shallow submarine and near‐coastal faults, using ...simulated seafloor pressures and a new catalog of SSEs in the Hikurangi subduction zone. We show that seafloor pressures may be represented by an average time history over the ~100‐km dimensions of the study area. We account for SSE uncertainties and the multiplicity of processes that affect SSEs statistically by estimating the probabilities of rejecting the null hypothesis that SSE initiation or termination pressures are those to be expected by chance sampling of known (modeled) seafloor pressures, with low probabilities indicating some causal connection. No impact of ocean pressure changes on SSE initiation is detectable, but a correlation with their terminations is suggested. SSE slip that weakens the fault and makes it more sensitive to small stress changes may explain results.
Plain Language Summary
The ocean waters may impart stresses that change how shallow submarine and near‐coastal faults start or stop slipping, particularly when they slip slowly over days to months (in episodes called slow slip events or SSEs). We can now assess this possibility using new simulated seafloor pressures and a catalog of SSEs in the Hikurangi subduction zone, encompassing the onshore and offshore region of northeastern New Zealand. We only ask how probable this causal connection is because SSEs are difficult to measure precisely and many physical processes may change their behaviors. Our statistical analyses do not reveal any impact of ocean pressure changes on how or when SSEs start, but do indicate they may affect when SSEs end. One explanation of this result is that the slow slippage actually causes the fault to become weaker, making it more sensitive to the small stress changes imparted by the ocean.
Key Points
Ocean water column changes may affect how and when Hikurangi shallow slow slip events end, but have no detectable impact on their starts
Transient slow slip events may weaken faults, making them more sensitive to small stress changes (<kPa)
Sparse noisy geodetic data and the emergent nature of slow slip events challenge generation of an accurate comprehensive regional catalog
We studied the earthquake detection capacity of DONET (Dense Oceanfloor Network system for Earthquakes and Tsunamis) operating in the Nankai Trough, a target region monitored for future megathrust ...earthquakes. The focus of this paper was to evaluate the impact on this capacity from the malfunction of parts of the network. For this purpose, the completeness magnitude, above which all earthquakes are considered to be detected by a seismic network, was used. Then, a catalog that includes events observed by DONET was used. We found spatiotemporal variability of completeness magnitude, ranging from values below 1 in one of the areas where stations are densely deployed to values above 2 at the periphery and outside of the DONET area. We conducted a simulation computation for cases of malfunction of densely distributed stations. The results showed that completeness estimates in the area near the malfunctioning stations were about 1 magnitude larger. This implies that malfunction repair and/or replacement with new stations would be desirable because they pronouncedly affect earthquake monitoring. We then demonstrated an example of how to use the information of completeness magnitude as prior knowledge to compute the
b
value of the Gutenberg-Richter distribution. The result indicates the
b
value as a proxy that can help to image stress heterogeneity when there is a magnitude-6 class slow slip event on the Nankai Trough plate boundary.
Several mutations in the surfactant protein C (SP-C) gene (SFTPC) have been reported as causing familial pulmonary fibrosis (FPF). However, the genetic background and clinical features of FPF are ...still not fully understood. We identified one Japanese kindred, in which at least six individuals over three generations were diagnosed with pulmonary fibrosis. We examined the patients radiologically and histopathologically and sequenced their SFTPC and ABCA3 genes. We also established a cell line stably expressing the mutant gene. All the patients had similar radiological and histopathological characteristics. Their histopathological pattern was that of usual interstitial pneumonia, showing numerous fibroblastic foci even in areas without abnormal radiological findings on chest high-resolution computed tomography. No child had respiratory symptoms in the kindred. Sequencing of SFTPC showed a novel heterozygous mutation, c.298G>A (G100S), in the BRICHOS domain of proSP-C, which co-segregated with the disease. However, in the ABCA3 gene, no mutation was found. In vitro expression of the mutant gene revealed that several endoplasmic reticulum stress-related proteins were strongly expressed. The mutation increases endoplasmic reticulum stress and induces apoptotic cell death compared with wild-type SP-C in alveolar type II cells, supporting the significance of this mutation in the pathogenesis of pulmonary fibrosis.
Since 2011, seafloor temperatures, pressures, and seismic ground motions have been measured by the seafloor cabled Dense Oceanfloor Network system for Earthquakes and Tsunamis (DONET) on the Nankai ...margin. These measurements, high‐resolution bathymetry, and abundant contextual information make the DONET region seem ideally suited to provide constraints on seismic shaking‐triggered sediment slope failures and gravity flows, particularly since numerous published studies have linked paleo‐ to modern earthquakes to failures and flows within the DONET. The occurrences of the local 2016 M6.0 Mie‐ken and regional M7.0 Kumamoto earthquakes within and at regional distances, respectively, from the DONET data set provided an opportunity to explore this potential. We used DONET seismic recordings of the posited triggering shaking and to search for submarine slide signals and continuous temperature and pressure data to detect pulses of warm and densified water indicative of passing flows. We developed and applied a variety of analytical methods to eliminate signals generated by water column processes, while leaving slope failures and sediment gravity flow anomalies as residuals. Our explorations yielded no evidence that earthquake shaking initiated either phenomenon, which we suggest reflects the finicky nature both of the detection of and the physical processes that contribute to slope failures and flows (i.e., both require satisfying precise suites of conditions). Nonetheless, this negative result, our analyses, and the estimates of physical properties we derived for them, provide useful lessons and inputs for future studies.
Plain Language Summary
Since 2011, measurements of both seafloor displacements caused by deformation within the Earth and motions of the water column above the seafloor have been made by the seafloor cabled Dense Oceanfloor Network system for Earthquakes and Tsunamis (DONET) in the offshore region of the Nankai subduction zone, Japan. These measurements, the occurrence in 2016 of a magnitude M6.0 earthquake within the DONET footprint and another M7.0 in southern Japan, and a rich repository of other information make the DONET region seem ideally suited to learn about how earthquake shaking triggers submarine landslides and rapidly flowing currents that carry sediments downslope. We analyzed DONET measurements but found no evidence that earthquake shaking initiated either phenomenon, which we suggest reflects the finicky nature both of detecting them and the physical processes that control their initiation. Nonetheless, our results provide useful lessons and inputs for future studies.
Key Points
New processing approaches reduce water column temperature and pressure influence, producing coherent, but propagating signatures
Generation and detection of slope failures and sediment gravity flows require satisfying multiple physical and observational criteria
No evidence of these phenomena within the Nankai Dense Oceanfloor Network system for Earthquakes and Tsunamis array despite plausible triggering shaking, environment, and history
A hypothetical influenza infection-induced non-specific immunity may reduce the risk of subsequent non-influenza respiratory virus (NIRV) infection and bias the influenza vaccine effectiveness (VE) ...estimates in test-negative designs (TNDs). We conducted a simulation study using a simple TND model and explored the degree of bias in the VE estimates. The bias was marginal during the usual seasons and most of the time during pandemics; the bias only became large when the influenza infection attack rate increased to pandemic levels (>50%), the true VE was low to moderate, and the non-specific immunity almost completely protected from NIRV infections and lasted at least half the influenza season.
Because of a lack of gold standard diagnostics, a combination of multiple diagnostic tests, or composite diagnostic standard, has been used to measure pneumococcal pneumonia (PP) in pneumococcal ...vaccine trials. We estimated the accuracy of composite diagnostic standards for PP used in previous randomised controlled trials by simple formulas. A systematic literature review identified five eligible trials and all trials had used different combinations of diagnostic tests for PP. The estimated values of sensitivity and minimum specificity of composite diagnostic standards varied substantially between trials: 48.4% to 98.1% and 71.0% to 97.3%, respectively. Without standardizing the outcome measurements, pneumococcal vaccine efficacy estimates against PP are not comparable between trials and their pooled estimates are biased.
OBJECTIVE: To investigate the prevalence of bacterial co-infection and its effect on early mortality among hospitalised human immunodeficiency virus (HIV) negative pulmonary tuberculosis (PTB) ...patients in Manila, the Philippines.DESIGN: A prospective observational study was conducted
at a national infectious disease hospital. HIV-negative PTB patients aged 13 years hospitalised from November to December 2011 and from December 2012 to May 2013 were enrolled. Sputum samples were tested for Mycobacterium tuberculosis and six respiratory bacterial pathogens using
polymerase chain reaction (PCR).RESULTS: Of 466 patients, 228 (48.9%) were TB-PCR-positive. Overall, bacterial pathogens in purulent sputum were detected in 135 (29.0%) patients: Haemophilus influenzae was the most common bacterium (21.2%), followed by Streptococcus pneumoniae
(7.9%). The prevalence of bacterial co-infection did not differ between TB-PCR-positive and -negative patients. A total of 92 (19.7%) patients died within 2 weeks. Bacterial co-infection was significantly associated with an increased risk of 2-week mortality among TB-PCR-positive patients
(adjusted risk ratio aRR 1.67, 95%CI 1.03-2.72). This association was also observed but did not reach statistical significance among TB-PCR-negative patients (aRR1.7, 95%CI 0.95-3.02).CONCLUSION: Bacterial co-infection is common and contributes to an increased risk of early mortality among HIV-negative PTB patients.
BACKGROUND: We investigated health-related quality of life (HrQoL) in Filipino people undergoing TB treatment, and whether HrQoL was negatively impacted by comorbidity with undernutrition, diabetes ...(DM) and anaemia.METHODS: Adult participants were enrolled in public
facilities in Metro Manila (three sites) and Negros Occidental (two sites). Multivariate linear regression was used to model the four correlated domain scores from a WHOQOL-BREF questionnaire (physical, psychological, social, environmental). A forward-stepwise approach was used to select a
final multivariable model with inclusion based on global tests of significance at P < 0.1.RESULTS: In 446 people on drug-susceptible TB treatment, DM and moderate/severe anaemia were not associated with HrQoL. After adjustment for age, sex, education, food insecurity,
treatment adherence, inflammation, Category I or II TB treatment, treatment phase, current side effects and inhibited ability to work, moderate/severe undernutrition (body mass index < 17 kg/m2) was associated with lower HrQoL (P = 0.003) with reduced psychological (coefficient:
−1.02, 95% CI −1.54 to −0.51), physical (−0.62, 95% CI −1.14 to −0.09) and environmental domain scores (−0.45, 95% CI −0.88 to −0.01). In 225 patients with known HIV status in Metro Manila, HIV was associated with modestly reduced HrQoL
(P = 0.014).CONCLUSION: Nutritional status and food insecurity represent modifiable risk factors for poor HrQoL that may be alleviated through interventions.
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