Development of an Epidemic‐type Aftershock‐sequence Model Explicitly Incorporating the Seismicity‐triggering Effects of Slow Slip Events

Slow slip events (SSEs) at subduction zone plate boundaries sometimes trigger earthquake swarms and megathrust earthquakes. The causal relationship between SSEs and seismicity has been studied worldwide, but the epidemic-type aftershock-sequence (ETAS) model, which is a standard statistical model of seismicity, does not explicitly consider the seismicity-triggering effect of SSEs. Therefore, if an SSE occurs at a plate boundary, probabilistic earthquake forecasts based on the ETAS model fail to predict observed seismicity. Here, we constructed a statistical model named the SSE-modulated ETAS model by incorporating SSE moment rates estimated from observation data from the global navigation satellite system into the original ETAS model. Our model assumes a linear or power-law relationship between the SSE moment rates and seismicity rates and estimates its proportionality constant as a new ETAS parameter. We applied this new model to three SSEs and M 2.5 or greater earthquakes in the shallow part of the Hikurangi Trench, New Zealand. The results show that it is better than the original ETAS model, giving a significant reduction in the Akaike information criterion. In addition, we examined the functional forms (e.g., lag time and power exponent) of the equation relating the moment rate of the SSEs to the seismicity rate. We also examine the influence of SSEs on aftershock productivity. Our model can improve short-term forecasts of seismicity associated with SSEs if the detection and characterization of SSEs can be done in near real time. Our model is also useful for quantifying characteristics of SSE-induced seismicity

Earthquake Swarm Detection Along the Hikurangi Trench, New Zealand: Insights Into the Relationship Between Seismicity and Slow Slip Events

Earthquake swarms, which are anomalous increases in the seismicity rate without a distinguishable mainshock, often accompany transient aseismic processes, such as fluid migration and episodic aseismic slip along faults. Investigations of earthquake swarm activity can provide insights into the causal relationship between aseismic processes and seismicity. Slow slip events (SSEs) along the plate interface in the Hikurangi Trench, New Zealand, are often accompanied by intensive earthquake swarms. However, the detailed spatiotemporal distribution of these earthquake swarms is still unclear. Here, we use the epidemic-type aftershock-sequence (ETAS) model to detect earthquake swarms (M ≥ 3) and create a new earthquake swarm catalog (1997–2015) along the Hikurangi Trench. We compare the earthquake swarm catalog with Global Navigation Satellite System (GNSS) time series data, and existing SSE and tectonic tremor catalogs. Most of the detected (119) earthquake swarm sequences were intraplate events, and their epicenters were mainly concentrated along the east coast of the North Island, whereas many tectonic tremors were located inland. Twenty-five of the detected earthquake swarms occurred within 25 days before and after transient eastward GNSS displacements due to known or newly detected SSEs. We find that the earthquake swarms sometimes preceded the GNSS displacements by more than several days. SSE-induced stress loading is therefore not a plausible triggering mechanism for these pre-SSE earthquake swarms. We propose that high fluid pressure within the slab, which accumulated before the SSEs, may have caused intraplate fluid migration, which in turn triggered the pre-SSE earthquake swarms

A review on slow earthquakes in the Japan Trench

Slow earthquakes are episodic slow fault slips. They form a fundamental component of interplate deformation processes, along with fast, regular earthquakes. Recent seismological and geodetic observations have revealed detailed slow earthquake activity along the Japan Trench—the subduction zone where the March 11, 2011, moment magnitude (Mw) 9.0 Tohoku-Oki earthquake occurred. In this paper, we review observational, experimental, and simulation studies on slow earthquakes along the Japan Trench and their research history. By compiling the observations of slow earthquakes (e.g., tectonic tremors, very-low-frequency earthquakes, and slow slip events) and related fault slip phenomena (e.g., small repeating earthquakes, earthquake swarms, and foreshocks of large interplate earthquakes), we present an integrated slow earthquake distribution along the Japan Trench. Slow and megathrust earthquakes are spatially complementary in distribution, and slow earthquakes sometimes trigger fast earthquakes in their vicinities. An approximately 200-km-long along-strike gap of seismic slow earthquakes (i.e., tectonic tremors and very-low-frequency earthquakes) corresponds with the huge interplate locked zone of the central Japan Trench. The Mw 9.0 Tohoku-Oki earthquake ruptured this locked zone, but the rupture terminated without propagating deep into the slow-earthquake-genic regions in the northern and southern Japan Trench. Slow earthquakes are involved in both the rupture initiation and termination processes of megathrust earthquakes in the Japan Trench. We then compared the integrated slow earthquake distribution with the crustal structure of the Japan Trench (e.g., interplate sedimentary units, subducting seamounts, petit-spot volcanoes, horst and graben structures, residual gravity, seismic velocity structure, and plate boundary reflection intensity) and described the geological environment of the slow-earthquake-genic regions (e.g., water sources, pressure–temperature conditions, and metamorphism). The integrated slow earthquake distribution enabled us to comprehensively discuss the role of slow earthquakes in the occurrence process of the Tohoku-Oki earthquake. The correspondences of the slow earthquake distribution with the crustal structure and geological environment provide insights into the slow-earthquake-genesis in the Japan Trench and imply that highly overpressured fluids are key to understanding the complex slow earthquake distribution. Furthermore, we propose that detailed monitoring of slow earthquake activity can improve the forecasts of interplate seismicity along the Japan Trench

Theory and Practice on the Implementation of Multilateral Environmental Agreements

国際環境法は,現代国際法の非常に新しい分野の一つとして,1970年以降急速に発展してきた.そして1992年のリオ会議を経て,その主要テーマは,立法から実施へと移り変わっている.多くの国際環境条約は,締約国会議を中心とした条約システムの中で,国家報告制度や遵守手続を備えている.本稿では、このような国際環境条約の実施に関する研究動向について概括し,特に遵守手続に関して,M.Koskenniemi (1993年), M.Fitzmaurice & C.Redgwell (2000年),そしてG.Loibl (2004年)の学説を紹介し,遵守手続の理論状況を分析する.その上で,国際環境条約の実施メカニズムの現状から導き出される一般国際法上との関係について検討する.最後に国際環境法のレジームとしての重複・抵触の問題を検討し,「持続可能な発展」概念を念頭に入れた国際環境法の統合の可能性について言及する.International Environmental Law is one of the new areas in modern international law and has been rapidly developing since 1972 Stockholm Conference. In the wake of 1992 Rio Conference, international community has shifted the emphasis from law-making to implementation in this field. Many Multilateral Environmental Agreements (MEAs) establish National Reporting system amd Non-Compliance Procedure in which the Conference of the Parties plays a central role. The first purpose of this review paper is to watch the moves of research about the implementation of MEAs, especially Non-Compliance Procedures. With acceptance on this point, it is the second work to research some problems on general international law in the current situation of the implementation systems of MEAs. At last, it seems important to deliberate on overlap or contradiction between MEAs, and I would like to mention the conditionality of the integration of international environmental law

Characteristics of Dredged Sludges by Desiccation

To examine the possible reuse of dredged sludge in view of construction material, physico-chemical properties and geotechnical characteristics of desiccated sludge are investigated through laboratory experiments. The consistency test, the pH test, the XRF test and the X-ray diffraction analysis are carried out for physico-chemical proteries, and the conolidation test and the permeability test are made for geotechnical characteristics. It is concluded that the history of desiccation changes the consistency of sludge and affects its permeability and consolidation bahavior

Effects of saliva collection using cotton swabs on melatonin enzyme immunoassay

<p>Abstract</p> <p>Background</p> <p>Although various acceptable and easy-to-use devices have been used for saliva collection, cotton swabs are among the most common ones. Previous studies reported that cotton swabs yield a lower level of melatonin detection. However, this statistical method is not adequate for detecting an agreement between cotton saliva collection and passive saliva collection, and a test for bias is needed. Furthermore, the effects of cotton swabs have not been examined at lower melatonin level, a level at which melatonin is used for assessment of circadian rhythms, namely dim light melatonin onset (DLMO). In the present study, we estimated the effect of cotton swabs on the results of salivary melatonin assay using the Bland-Altman plot at lower level.</p> <p>Methods</p> <p>Nine healthy males were recruited and each provided four saliva samples on a single day to yield a total of 36 samples. Saliva samples were directly collected in plastic tubes using plastic straws, and subsequently pipetted onto cotton swabs (cotton saliva collection) and into clear sterile tubes (passive saliva collection). The melatonin levels were analyzed in duplicate using commercially available ELISA kits.</p> <p>Results</p> <p>The mean melatonin concentration in cotton saliva collection samples was significantly lower than that in passive saliva collection samples at higher melatonin level (>6 pg/mL). The Bland-Altman plot indicated that cotton swabs causes relative and proportional biases in the assay results. For lower melatonin level (<6 pg/mL), although the BA plots didn't show proportional and relative biases, there was no significant correlation between passive and cotton saliva collection samples.</p> <p>Conclusion</p> <p>Our findings indicate an interference effect of cotton swabs on the assay result of salivary melatonin at lower melatonin level. Cotton-based collection devices might, thus, not be suitable for assessment of DLMO.</p

Observation of the distortion around Ga lattice sites due to the residual hydrogen in GaN single crystal wafer

In RBS channeling experiments, the slight de-channeling phenomenon of Ga was observed from the depth of about 250 nm in depth behind the surface peak in un-annealed GaN single crystal wafers. In ERDA experiments using 1.8 MeV He^4+ beam, the hydrogen concentration (4.8 x 10^14 cm^-2) in un-annealed GaN was about the twice of that in 900 oC annealed one, suggesting that part of the residual hydrogen was out diffused by annealing. The existence of the minute displacement of Ga in un-annealed GaN was associated with the Ga displacement arising from the complex defect of the residual hydrogen and Ga. This phenomenon corresponds to the appreciable relaxation of Ga atoms toward H proposed by Myer et al. The slight de-channeling phenomena of the Ga atom observed in the RBS channeling experiment disappeared in association with the reduction of hydrogen due to out diffusion of hydrogen in the annealed wafer

Highly Active Ni- and Co-Based Bimetallic Catalysts for Hydrogen Production From Ammonia-Borane

Ammonia-borane is one of the most promising candidates for hydrogen carriers. A series of Ni- and Co-based bimetallic catalysts supported on SiO2 (Ni–M/SiO2 and Co–M/SiO2; M = Ga, Ge, Sn, Zn) was prepared and tested as catalysts for hydrogen production from ammonia-borane (AB) in water or methanol. Ni–Zn/SiO2 and Co–Ge/SiO2 exhibited catalytic activities much higher than those of monometallic Ni/SiO2 and Co/SiO2, respectively. Ni–Zn/SiO2 showed a high catalytic activity when water was used as a solvent, where the reaction was completed within 6 min at room temperature with a specific reaction rate of 4.3 ml min−1 mmol-cat−1 mM-AB−1. To the best of our knowledge, this is the highest value among those reported using 3d metal-based catalysts. Co–Ge/SiO2 afforded a five-fold higher reaction rate than that of the corresponding monometallic Co/SiO2. XRD, TEM, and HAADF-STEM-EDS analyses revealed that Ni0.75Zn0.25 and Co0.8Ge0.2 solid-solution alloys were formed with high phase purities. An XPS study showed that Co atoms in Co0.8Ge0.2 were electron-enriched due to electron transfer from Ge to Co, which may be the origin of the improved catalytic activity