Seismological Structures on Bimodal Distribution of Deep Tectonic Tremor

Deep tectonic tremors occur at the downdip extent of the seismogenic zone due to fluid processes. Beneath the northeastern Kii Peninsula, southwestern Japan, there is an along-dip bimodal distribution of tremor. However, no constraint exists on the structures controlling that distribution. We extract detailed seismological structures from multi-band receiver functions and evaluate conditional differences in the distribution. To achieve high resolution images along the plate interface, we utilize records of regional deep-focus earthquakes from the Pacific slab. Cross-section images show the subducting oceanic plate with depth-dependent phases along the bimodal distribution, revealing a conspicuous plate interface at the updip portion and an inconspicuous interface below the mantle wedge at the downdip portion. This indicates that episodic tremors occur in the high pore-fluid plate interface below the impermeable forearc crust, and that continual tremors occur at the permeable mantle wedge corner, owing to continuous fluid supply from the oceanic crust. [Plain Language Summary] Deep slow earthquakes have mainly been detected at the deeper extent of estimated large-slip regions of large-scale regular earthquakes in the Nankai subduction zone, southwestern Japan. Epicenters of tectonic tremors are also downdip-aligned. However, some clusters of continual tremor with frequent small bursts were found at further downdip portions beneath the northeastern Kii Peninsula. The complexity of the bimodal tremor distribution poses a structural question regarding whether the tectonic tremor occurs below a mantle wedge or below the continental crust. We utilize a receiver function method that surveys subsurface velocity boundaries and evaluate detailed seismological structures around the plate interface using a multi-band analysis. Furthermore, regional deep-focus earthquake records are effectively utilized for receiver function mapping. The high-frequency cross section exhibits depth dependence of plate-interface phases, which demarcates active regions of updip events and downdip continual tremor, thus revealing that episodic tremor occurs below the continental crust and continual tremor occurs at the mantle wedge corner. The high-contrast updip interface reveals that a large amount of fluid is confined at the plate interface below the impermeable forearc crust, which may lead to active episodic slow earthquakes at updip portions

Simultaneous high-performance liquid chromatographic determination of 6β-hydroxycortisol and cortisol in urine with fluorescence detection and its application for estimating hepatic drug-metabolizing enzyme induction

A simple and sensitive high-performance liquid chromatographic method is described for the simultaneous determination of 6β-hydroxycortisol (6β-OHF) and cortisol (F) in urine. Urine (1 ml) containing fludrocortisone as the internal standard is extracted with ethyl acetate. The extract is washed successively with sodium hydroxide solution and water, and subsequently dried under a stream of nitrogen. The residue is redissolved in methanol. The 6β-OHF, F and fludrocortisone in the methanol solution are oxidized by cupric acetate and the resulting glyoxal compounds are converted into fluorescent derivatives with 1,2-diamino-4,5-methylenedioxybenzene (DMB). The DMB derivatives of the corticosteroids are separated within 70 min on a reversed-phase column, L-Column ODS, using stepwise elution with methanol—acetonitrile—0.5 M ammonium acetate and detected fluorimetrically at 350 nm (excitation) and 390 nm (emission). The lower limits of detection for 6β-OHF and F are 1.8 pmol (680 pg) and 2.4 pmol (950 pg)/ml urine (0.6 pmol and 0.8 pmol/100 μl injection volume), respectively, at a signal-to-noise ratio of 3. This method can be applied to the determination of urinary 6β-OHF, and the ratio of 6β-OHF to F in humans and in rhesus monkeys treated orally with phenobarbital as a hepatic drug-metabolizing enzyme inducer

The Key Factors to Maintain IADL among Japanese Elderly — From the View-point of Bone Quality—

Objective: Bone quality (Stiffness Index: SI) approach to elderly osteoporosis has been accelerating interest in recent years. However, there are few data on the relation between SI and instrumental activities of daily living (IADL). The objective of this study is to present the effective target to maintain IADL among Japanese elderly from the view-point of SI. Methods: SI and IADL-related physical measurement items, such as age, body mass index (BMI), fat mass, muscle mass, hand-grip strength, daily energy expenditure, daily movements, daily steps, maximum walking speed (MWS), usual walking speed (UWS) and maximum bite force (MBF) were examined on Japanese elderly aged≧60-year-old. The data of 374 subjects (134 male, 240 female) were analyzed. Results: Stepwise multiple regression showed that male UWS (standardized regression coefficient β=0.27) and female BMI (β=0.27) were the best predictors of SI. Simple regression analysis showed significant positive linear relation of male UWS and female BMI to SI. Conclusion: SI can be a persuasive tool for indirect IADL evaluation via male UWS and female BMI. From the view-point of SI, we propose that male SI>82.5 and female SI>55.6 are the key factors to maintain IADL keeping male UWS>1.39 m/sec and female BMI>22