Seismic vertical array analysis for phase decomposition     

Kunikazu Yoshida  Tsutomu Sasatani 《Geophysical Journal International》2008,174(2):707-718

We propose a vertical array analysis method that decomposes complex seismograms into body and surface wave time histories by using a velocity structure at the vertical array site. We assume that the vertical array records are the sum of vertically incident plane P and S waves, and laterally incident Love and Rayleigh waves. Each phase at the surface is related to that at a certain depth by the transfer function in the frequency domain; the transfer function is obtained by Haskell's matrix method, assuming a 1-D velocity structure. Decomposed P , S and surface waves at the surface are estimated from the vertical array records and the transfer functions by using a least-squares method in the frequency domain; their time histories are obtained by the inverse Fourier transform. We carried out numerical tests of this method based on synthetic vertical array records consisting of vertically incident plane P and S waves and laterally incident plane Love and Rayleigh waves. Perfect results of the decomposed P , S , Love and Rayleigh waves were obtained for synthetic records without noise. A test of the synthetic records in which a small amount of white noise was added yielded a reasonable result for the decomposed P , S and surface waves. We applied this method to real vertical array records from the Ashigara valley, a moderate-sized sedimentary valley. The array records from two earthquakes occurring at depths of 123 and 148 km near the array (epicentral distance of about 31 km) exhibited long-duration later phases. The analysis showed that duration of the decomposed S waves was a few seconds and that the decomposed surface waves appeared a few seconds after the direct S -wave arrival and had very long duration. This result indicated that the long-duration later phases were generated not by multireflected S waves, but by basin-induced surface waves.  相似文献   

Global distributions of storm-time ionospheric currents as seen in geomagnetic field variations     

Atsuki Shinbori  Tomoaki Hori  Yoshimasa Tanaka  Yukinobu Koyama  Takashi Kikuchi  Tsutomu Nagatsuma 《极地研究(英文版)》2013,(4):296-314

To investigate temporal and spatial evolution of global geomagnetic field variations from high-latitude to the equator during geomagnetic storms, we analyzed ground geomagnetic field disturbances from high latitudes to the magnetic equator. The daytime ionospheric equivalent current during the storm main phase showed that twin-vortex ionospheric currents driven by the Region 1 field-aligned currents （R1 FACs） are intensified significantly and expand to the low-latitude region of-30~ magnetic latitude. Centers of the currents were located around 70~ and 65~ in the morning and afternoon, respectively. Corresponding to intensification of the R1 FACs, an enhancement of the eastward/westward equatorial electrojet occurred at the daytime/nighttime dip equator. This signature suggests that the enhanced convection electric field penetrates to both the daytime and nighttime equa- tor. During the recovery phase, the daytime equivalent current showed that two new pairs of twin vortices, which are different from two-cell ionospheric currents driven by the R1 FACs, appear in the polar cap and mid latitude. The former led to enhanced north- ward Bz （NBZ） FACs driven by lobe reconnection tailward of the cusps, owing to the northward interplanetary magnetic field （IMF）. The latter was generated by enhanced Region 2 field-aligned currents （R2 FACs）. Associated with these magnetic field variations in the mid-latitudes and polar cap, the equatorial magnetic field variation showed a strongly negative signature, produced by the westward equatorial electrojet current caused by the dusk-to-dawn electric field.  相似文献   

Can the visualization of rip currents prevent drowning accidents? Consideration of the effect of optimism bias     

Endo  Shintaro  Shimada  Ryo  Ishikawa  Toshinori  Komine  Tsutomu 《Natural Hazards》2022,110(3):2017-2033

Drowning accidents at beach in Japan are caused by rip currents. To reduce these accidents, a new technology that can detect rip currents and notify beachgoers by using the Internet of Things (IoT) and Artificial Intelligence (AI) was proposed. However, studies on the effect of visualizing rip currents or considering the effect of optimism bias have not been conducted. This study investigates if visualization of rip currents might help in preventing drowning accidents, while considering the effect of optimism bias. The participants were 90 Japanese beachgoers. They were asked to answer questions based on their knowledge of the beach and rip currents, their optimism bias regarding rip currents, and awareness with or without visualization. The results of the analyses suggest that despite optimism bias, the visualization of rip currents increases the tendency of beachgoers to perceive and avoid rip currents. As described above, it was found that by visualizing the rip current, beachgoers were able to perceive and avoid rip currents. In addition, an understanding of rip currents is positively related to the intent to avoid rip currents even when rip currents are visualized. Therefore, it is necessary not only to enhance the avoidance tendency by visualizing rip currents, but also to further enhance knowledge of beachgoers to deepen the understanding of rip currents including the danger associated and methods to avoid them.

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New scenario of turbulence theory and wall-bounded turbulence: theoretical significance     

Tsutomu Kambe 《地球物理与天体物理流体动力学》2017,111(6):448-507

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Interaction of energetic particles with HM-waves in the magnetosphere     

Tsutomu Tamao 《Planetary and Space Science》1984,32(11):1371-1386

Energetic particle response in electromagnetic fields of ULF HM-waves in the magnetosphere is reviewed. Pc4–5 geomagnetic pulsations observed at the synchronous altitude are classified into three types, in respect to their major magnetic field polarization in different directions, local time dependence, and different characteristics of accompanied flux modulations of energetic particles, i.e., two nearly transverse waves with the azimuthal and the radial polarization, and the compressional stormtime pulsations. Firstly, we formulate the drift kinetic theory of particle flux modulations under the constraint of the magnetic moment conservation. A generalized energy integral of the particle motion interacting with a ULF-wave with the three-dimensional structure propagating to the azimuthal direction is obtained in the L-shell coordinate of a mirror magnetic field. Its linearized form is reduced to the same form as the previously derived energy change, including the bounce-drift resonant interaction. It is shown that the perturbed guiding center distribution function of energetic particles consists of four contributions, the adiabatic mirror effect corresponding to pitch-angle change, the kinetic effects due to energy change and the accompanying L-shell displacement, and the bounceaveraged drift phase bunching. Secondly, the basic HM-wave modes constitutingcoupling ULF oscillations in non-uniform plasmas are discussed in different models of approach for different plasma states. The diamagnetic drift Alfvén wave and the compressional drift wave with a larger azimuthal mode number in a high-beta plasma are candidates for the stormtimes pulsations. The former is intrinsically a guided localized mode, while the latter is a non-localized mode. By making use of the above preparation, we apply the developed drift kinetic theory to interpret the phase relationships between the ion flux modulation and the geomagnetic pulsation in some selected examples of observations, demonstrating a fair agreement in theoretical results with the observations.  相似文献   

A practical model to estimate photosynthetically active radiation using general meteorological elements in a temperate humid area and comparison among models     

Yasuko Mizoguchi  Yukio Yasuda  Yoshikazu Ohtani  Tsutomu Watanabe  Yuji Kominami  Katsumi Yamanoi 《Theoretical and Applied Climatology》2014,115(3-4):583-589

Although accurately evaluating photosynthetically active radiation is important, much effort is required to measure this radiation using a quantum sensor. We develop a new model that makes estimates using only general meteorological data—solar radiation, atmospheric pressure, air temperature, and relative humidity. Root mean square deviations for eight datasets at five sites in Japan were smaller than 5.2 %, similar to error in other studies and to individual differences of quantum sensors. Most root mean square deviations of nine previous models and our eight datasets are larger than that of the new estimation model, which performed well. This suggests that the model is useful for estimating photosynthetically active radiation in a temperate, humid area of Japan.  相似文献   

Metabolism and chemical composition of marine pelagic gastropod molluscs: a synthesis     

Tsutomu Ikeda 《Journal of Oceanography》2014,70(3):289-305

Metabolism (respiration and ammonia excretion rates) and chemical composition data [water content, ash, carbon (C), nitrogen (N) and C:N ratios] of a total of between 6–32 species of pteropods (thecosomes and gymnosomes) and heteropods from ≤500 m depth of the world’s oceans were compiled. Among the independent variables designated (body mass, habitat temperature, sampling depth, taxon), body mass and habitat temperature were significant predictors of metabolism, attributing to 85 % of the variance in respiration rates and 69 % of the variance in ammonia excretion rates. Atomic O:N ratios (respiration:ammonia excretion) ranged from 7.0 to 100 (median 14.5), and no appreciable effects of the variables were detected. A significant negative correlation of C and N compositions and habitat temperature was seen only in the thecosomes. As judged by the concomitant increase in C:N ratios with increasing habitat temperature, a greater deposition of inorganic C (as CaCO₃–C) in the shell of the warmer-living species was suggested. Compared with other zooplankton (copepods, chaetognaths, and euphausiids), the thecosomes were characterized by higher respiration rates per unit body N and larger ash content by having possession of calcareous shells. Because of the shells, C and N composition expressed as % of dry mass of the thecosomes were lower than those of the other zooplankton taxa.  相似文献   

Empirical analysis of path effects on prediction equations of pseudo‐velocity response spectra in northern Japan     

Yadab P. Dhakal  Nobuo Takai  Tsutomu Sasatani 《地震工程与结构动力学》2010,39(4):443-461

We study path effects on prediction equations of pseudo‐velocity response spectra (natural period of 0.1–5.0 s) in northern Japan, where heterogeneous attenuation structure exists. The path effects have been examined by comparing the regression analysis results for two different prediction equations. The first equation consists of a single term of anelastic attenuation conventionally. The second equation consists of two terms of anelastic attenuation in consideration of the heterogeneous attenuation structure. In the second equation, we divide a source‐to‐site distance into two distances at the attenuation boundary beneath the volcanic front. The boundary is considered to separate the relatively high Q fore‐arc side mantle wedge (FAMW) from the low Q back‐arc side mantle wedge (BAMW). Strong motion records (hypocentral distances less than 300 km) from interplate and intraslab events with Mw 5.1–7.3 are used. Regression analysis results show that the standard errors are significantly reduced by the second prediction equation at short periods (0.1–0.5 s), whereas the difference in standard errors from both prediction equations is negligible at intermediate and long periods. The Qs values (quality factor for S‐wave) converted from two anelastic attenuation coefficients for the second prediction equation are remarkably similar to the path‐averaged Qs values for the FAMW and BAMW by other studies using spectral inversion method. From these findings, we conclude that the path effects on the prediction equation of pseudo‐velocity response spectra are satisfactorily accomplished by the second prediction equation. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Surface mass balance on Glacier No. 31 in the Suntar–Khayata Range,eastern Siberia,from 1951 to 2014     

Yong Zhang  Hiroyuki Enomoto  Tetsuo Ohata  Tsutomu Kadota  Tatsuo Shirakawa  Nozomu Takeuchi 《山地科学学报》2017,14(3):501-512

This study presents a 64-year(1951–2014) reconstruction of the surface mass balance of Glacier No. 31, located in the Suntar-Khayata Range of the eastern Siberia, where the ablation zone is characterized by the extensive dark ice surface. We use a temperature index-based glacier mass-balance model, which computes all major components of glacier mass budget and is forced by daily air temperature and precipitation from a nearby meteorological station. The glacier shows a mean annual mass balance of –0.35 m w.e.a~(–1) during the past 64 years, with an acceleration of –0.50 m w.e. a~(–1) during the recent years. A cumulative mass loss of the glacier is ~22.3 m w.e. over the study period, about 56% of which is observed during 1991–2014. In addition to the contribution of temperature rise and precipitation decrease to recent mass loss of the glacier, an experimental analysis, in which the cleanand dark ice surfaces are respectively assumed to cover the entire ablation zone, indicates that dark ice surface, caused by insoluble impurities consisting of mineral dusts, cryoconite granules, and ice algae, plays a crucial role in the changing mass balance through enhancing melt rates in the ablation zone of the glacier.  相似文献   

Boron cycling by subducted lithosphere; insights from diamondiferous tourmaline from the Kokchetav ultrahigh-pressure metamorphic belt     

Tsutomu Ota  Katsura Kobayashi  Takuya Kunihiro  Eizo Nakamura 《Geochimica et cosmochimica acta》2008,72(14):3531-3541

Subduction of lithosphere, involving surficial materials, into the deep mantle is fundamental to the chemical evolution of the Earth. However, the chemical evolution of the lithosphere during subduction to depth remains equivocal. In order to identify materials subjected to geological processes near the surface and at depths in subduction zones, we examined B and Li isotopes behavior in a unique diamondiferous, K-rich tourmaline (K-tourmaline) from the Kokchetav ultrahigh-pressure metamorphic belt. The K-tourmaline, which includes microdiamonds in its core, is enriched in ¹¹B relative to ¹⁰B (δ¹¹B = −1.2 to +7.7) and ⁷Li relative to ⁶Li (δ⁷Li = −1.1 to +3.1). It is suggested that the K-tourmaline crystallized at high-pressure in the diamond stability field from a silicate melt generated at high-pressure and temperature conditions of the Kokchetav peak metamorphism. The heavy isotope signature of this K-tourmaline differs from that of ordinary Na-tourmalines in crustal rocks, enriched in the light B isotope (δ¹¹B = −16.6 to −2.3), which experienced isotope fractionation through metamorphic dehydration reactions. A possible source of the heavy B-isotope signature is serpentine in the subducted lithospheric mantle. Serpentinization of the lithospheric mantle, with enrichment of heavy B-isotope, can be produced by normal faulting at trench-outer rise or trench slope regions, followed by penetration of seawater into the lithospheric mantle. Serpentine breakdown in the lithospheric mantle subducted in subarc regions likely provided fluids with the heavy B-isotope signature, which was acquired during the serpentinization prior to subduction. The fluids could ascend and cause partial melting of the overlying crustal layer, and the resultant silicate melt could inherit the heavy B-isotope signature. The subducting lithospheric mantle is a key repository for modeling the flux of fluids and associated elements acquired at a near the surface into the deep mantle.  相似文献