Focal mechanisms and aftershock locations of the Songpan earthquakes of August 1976 in Sichuan, China

The precursory swarm, three mainshocks (M = 7.2,6.7, 7.2), and aftershocks of the Songpan earthquakes have been reanalyzed using both local and teleseismic data. The three mainshocks of this sequence occurred on the Huya fault over a 7-day period. Relocations of the aftershocks using local arrival times show that three fault strands were activated during this sequence. Each mainshock occurred on a separate strand, each one south of the strand activated in the previous mainshock, and the aftershock zones of each mainshock appear to abut rather than overlap. Fault plane solutions determined by matching teleseismic P waveforms at World-Wide Standard Seismograph Network stations with synthetic seismograms are consistent with the observed aftershock zones. The first and third mainshocks (M_0 = 1.3 ×10^(19) and 8.4 × 10^(18) N m, respectively) showed almost identical senses of motion, a combination of reverse and left-lateral strike-slip motion, on parallel strands, striking N15°W, that were separated by a large rightstepping en echelon offset. The second mainshock (M_0 = 4.0 × 10^(18) N m), occurred in this offset on a fault at a steep angle (∼125°) to the other two strands and showed almost pure reverse motion. Differences in the orientations of the slip vectors of the three mainshocks show that the first mainshock increased the normal and shear stresses on the fault segment that moved in the second mainshock and that the second mainshock decreased the normal stress on the fault segment activated by the third mainshock. These changes in normal stresses may have given rise to the longer time between the first and second events (5 days) as compared with the time between the second and third events (30 hours). A precursory swarm that preceded the Songpan sequence by 3 years occurred in a volume that surrounded the northernmost part of the planar aftershock zone. The time between the start of the swarm and the mainshocks and the magnitude of the largest event in the swarm are similar to those seen for precursory swarms in Soviet Central Asia

The MAGPI Survey: Effects of Spiral Arms on Different Tracers of the Interstellar Medium and Stellar Populations at z~0.3

Spiral structures are important drivers of the secular evolution of disc galaxies, however, the origin of spiral arms and their effects on the development of galaxies remain mysterious. In this work, we present two three-armed spiral galaxies at z~0.3 in the Middle Age Galaxy Properties with Integral Field Spectroscopy (MAGPI) survey. Taking advantage of the high spatial resolution (~0.6'') of the Multi-Unit Spectroscopic Unit (MUSE), we investigate the two-dimensional distributions of different spectral parameters: Halpha, gas-phase metallicity, and D4000. We notice significant offsets in Halpha (~0.2 dex) as well as gas-phase metallicities (~0.05 dex) among the spiral arms, downstream and upstream of MAGPI1202197197 (SG1202). This observational signature suggests the spiral structure in SG1202 is consistent with arising from density wave theory. No azimuthal variation in Halpha or gas-phase metallicities is observed in MAGPI1204198199 (SG1204), which can be attributed to the tighter spiral arms in SG1204 than SG1202, coming with stronger mixing effects in the disc. The absence of azimuthal D4000 variation in both galaxies suggests the stars at different ages are well-mixed between the spiral arms and distributed around the disc regions. The different azimuthal distributions in Halpha and D4000 highlight the importance of time scales traced by various spectral parameters when studying 2D distributions in spiral galaxies. This work demonstrates the feasibility of constraining spiral structures by tracing interstellar medium (ISM) and stellar population at z~0.3, with a plan to expand the study to the full MAGPI survey.Comment: 15 pages, 11 figures, 2 tables, accepted for publication in MNRA

断層帯構造と地震過程との関連 - システムは規模依存性を示すか

京都大学0048新制・論文博士博士(理学)乙第10363号論理博第1379号新制||理||1179(附属図書館)UT51-2000-F429(主査)教授 安藤 雅孝, 教授 竹本 修三, 教授 尾池 和夫学位規則第4条第2項該当Doctor of ScienceKyoto UniversityDA

Digital database construction for earthquake waveforms from analogue tape records

地震予知研究センターではセンター設立以前を含め30年以上の地震の記録が存在する。今回はその中でデータ処理を行えば現在のデータと同様に扱うことが可能なアナログMTのデータのAD変換及びデータ変換処理を行い波形データベースに組み込むことを目指した。対象としたのは上宝観測所の1977年8月から1993年7月まで16年間約1, 000巻のMTで、これらを高速一括変換した後, データを変換するソフトウェアの開発しwinプログラムで利用可能なデータベースを作成した。Analog data of seismic wave are stored for longterm more than 20 years in the observatories of Reaserch Center for Earthquake Prediction. In order to digitize and convert a large quantity of data, new operation and software for converting to digital records are developped. Using thi oreration and software More than 1, 000 MT records which is accumulated in the Karnitakara observatory in 16 years until July, 1993 from August, 1977 were processed. Constructed digital data files are easily used and analized by win program.地震予知研究センターではセンター設立以前を含め30年以上の地震の記録が存在する。今回はその中でデータ処理を行えば現在のデータと同様に扱うことが可能なアナログMTのデータのAD変換及びデータ変換処理を行い波形データベースに組み込むことを目指した。対象としたのは上宝観測所の1977年8月から1993年7月まで16年間約1,000巻のMTで、これらを高速一括変換した後,データを変換するソフトウェアの開発しwinプログラムで利用可能なデータベースを作成した。Analog data of seismic wave are stored for longterm more than 20 years in the observatories of Reaserch Center for Earthquake Prediction. In order to digitize and convert a large quantity of data, new operation and software for converting to digital records are developped. Using thi oreration and software More than 1,000 MT records which is accumulated in the Karnitakara observatory in 16 years until July, 1993 from August, 1977 were processed. Constructed digital data files are easily used and analized by win program

Effect of degumming time on silkworm silk fibre for biodegradable polymer composites

Recently, many studies have been conducted on exploitation of natural materials for modern product development and bioengineering applications. Apart from plant-based materials (such as sisal, hemp, jute, bamboo and palm fibre), animal-based fibre is a kind of sustainable natural materials for making novel composites. Silkworm silk fibre extracted from cocoon has been well recognized as a promising material for bio-medical engineering applications because of its superior mechanical and bioresorbable properties. However, when producing silk fibre reinforced biodegradable/bioresorbable polymer composites, hydrophilic sericin has been found to cause poor interfacial bonding with most polymers and thus, it results in affecting the resultant properties of the composites. Besides, sericin layers on fibroin surface may also cause an adverse effect towards biocompatibility and hypersensitivity to silk for implant applications. Therefore, a proper pre-treatment should be done for sericin removal. Degumming is a surface modification process which allows a wide control of the silk fibre's properties, making the silk fibre possible to be used for the development and production of novel bio-composites with unique/specific mechanical and biodegradable properties. In this paper, a cleaner and environmentally friendly surface modification technique for tussah silk in polymer based composites is proposed. The effectiveness of different degumming parameters including degumming time and temperature on tussah silk is discussed through the analyses of their mechanical and morphological properties. Based on results obtained, it was found that the mechanical properties of tussah silk are affected by the degumming time due to the change of the fibre structure and fibroin alignment