T. Kunugi, S. Aoi, H. Nakamura, W. Suzuki, N. Morikawa, H. Fujiwara
We present an improved implementation of the approximating fi lter for real-time seismic intensity calculations proposed in previous work. As earthquake early warning (EEW) systems become ever more widely used, the current method of computing a JMA (Japan Meteorological Agency) seismic intensity shows a serious problem since it introduces a time delay resulting from frequency domain fi ltering. In order to improve this method to permit real-time calculations suitable for EEW systems, we have proposed a real-time seismic intensity computed using an approximating fi lter in the time domain. For a simple computing system such as a strong-motion seismograph, it is straightforward to calculate the real-time seismic intensity because the approximating fi lter consists of only four fi rst-order fi lters and one secondorder fi lter. Based on testing using K-NET and KiK-net strong-motion seismographs, we have found that a strong-motion seismograph has enough computational capacity to undertake more sophisticated fi ltering. Here, we develop an approximating fi lter consisting of six second-order fi lters applied in the time domain for accurate real-time seismic intensity calculation. The relationship between the JMA seismic intensity and the real-time seismic intensity calculated using the improved approximating fi lter is examined using a large number of strong motion records. The results show that the diff erences between the JMA seismic intensities and the real-time seismic intensities are less than 0.1 for 99% of all records. Although the improved fi lter requires twice as much computation power as the previous approximating fi lter, it is suitable for EEW systems that require more accurate real-time calculations of seismic intensity.
{"title":"An Improved Approximating Filter for Real-Time Calculation of Seismic Intensity","authors":"T. Kunugi, S. Aoi, H. Nakamura, W. Suzuki, N. Morikawa, H. Fujiwara","doi":"10.4294/ZISIN.65.223","DOIUrl":"https://doi.org/10.4294/ZISIN.65.223","url":null,"abstract":"We present an improved implementation of the approximating fi lter for real-time seismic intensity calculations proposed in previous work. As earthquake early warning (EEW) systems become ever more widely used, the current method of computing a JMA (Japan Meteorological Agency) seismic intensity shows a serious problem since it introduces a time delay resulting from frequency domain fi ltering. In order to improve this method to permit real-time calculations suitable for EEW systems, we have proposed a real-time seismic intensity computed using an approximating fi lter in the time domain. For a simple computing system such as a strong-motion seismograph, it is straightforward to calculate the real-time seismic intensity because the approximating fi lter consists of only four fi rst-order fi lters and one secondorder fi lter. Based on testing using K-NET and KiK-net strong-motion seismographs, we have found that a strong-motion seismograph has enough computational capacity to undertake more sophisticated fi ltering. Here, we develop an approximating fi lter consisting of six second-order fi lters applied in the time domain for accurate real-time seismic intensity calculation. The relationship between the JMA seismic intensity and the real-time seismic intensity calculated using the improved approximating fi lter is examined using a large number of strong motion records. The results show that the diff erences between the JMA seismic intensities and the real-time seismic intensities are less than 0.1 for 99% of all records. Although the improved fi lter requires twice as much computation power as the previous approximating fi lter, it is suitable for EEW systems that require more accurate real-time calculations of seismic intensity.","PeriodicalId":332254,"journal":{"name":"Journal of the Seismological Society of Japan","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128786047","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
H. Takaoka, N. Tsumura, F. Takahashi, K. Nozaki, A. Kato, T. Iidaka, T. Iwasaki, Sakai Shin’ichi, N. Hirata, R. Ikuta, T. Kunitomo, Y. Yoshida, K. Katsumata, K. Yamaoka, Toshiki Watanabe, F. Yamazaki, M. Okubo, Sadaomi Suzuki
Long term slow slip (LTSS) and non-volcanic low frequency earthquakes (LFEs) were reported in the central part of the Tokai district, central Japan. Such LTSS and LFE events are considered to take place at transition zone from stick-slip zone to stable sliding zone and to be associated with fluids on the subducting Philippine Sea plate’s surface. To clarify the spatial variation of the physical properties in this region, we estimated a three dimensional seismic attenuation structure using joint inversion method. In this study, we used 3688 spectra of 140 earthquakes which were observed by both temporary stations conducted from April to August in 2008 and permanent stations. Frequency band was divided equally among 24 between 0.78125 and 18.75 Hz and equally among 8 between 18.75 and 31.25 Hz. We gave Q blocks by dividing study area into 7 in the N-S direction between 137E and 138.5E degree, into 6 blocks in E-W direction between 34.5N and 35.7N, and 6 depth layers. We estimated frequency independent Q value of each block. In Q zone located along the Median tectonic line which divides the southwestern Japan into two parts; a old geologic belt and a new accretionary belt. In the lower crust of the land plate at the depths of 17 to 25km, a very high Q zone (about 2000) exists just above the region where large slip rate was observed in LTSS between 2001 and 2005. Since very few earthquakes occur in this high Q zone, that portion might consist of harder rocks than surroundings. On the contrary, the region just beneath the large slip zone has lower Q than surrounding area. Comparing our results with the seismic velocity structure derived from travel time tomography, we found the high Q zone approximately coincides with relatively high velocity zone, and lower Q zone corresponds to the relatively low velocity and high Vp/Vs region. As mentioned in previous studies, low Q zone with low velocity and high Vp/Vs is interpreted as the zone which involves high-pressure fluid. Probably the high Q zone above the large slip zone works as a cap rock and prevents the fluid moving toward the shallow part, then the fluid pressure becomes high and it affects the occurrence of slow slip in this region. Slow earthquakes called episodic tremor and slip (ETS) propagate over 100 kilometers at low velocities, ˜10 kilometers per day, along several plate interfaces. These low velocities differentiate slow earthquakes from ordinary earthquakes, and thus understanding their propagation processes is fundamental to understand the diversity and universality of earthquake processes. Com-prehensive modeling and previously-unreported correlations of migration patterns with energetics of tremor observed in Japan show that rheological fault heterogeneity essentially governs ETS propagations. The fault has persistent small-scale segmenta-tion, where the propagations always energetically started in brittle sections and decelerated in the ductile sections; spontaneous rupture calculations co
微裂纹的形成消耗了断裂扩展的能量。因此，非断层微裂纹是重要的和有效的
{"title":"Three-dimensional Attenuation Structure beneath the Tokai Region, Central Japan Derived Using Local Earthquake Spectra","authors":"H. Takaoka, N. Tsumura, F. Takahashi, K. Nozaki, A. Kato, T. Iidaka, T. Iwasaki, Sakai Shin’ichi, N. Hirata, R. Ikuta, T. Kunitomo, Y. Yoshida, K. Katsumata, K. Yamaoka, Toshiki Watanabe, F. Yamazaki, M. Okubo, Sadaomi Suzuki","doi":"10.4294/ZISIN.65.175","DOIUrl":"https://doi.org/10.4294/ZISIN.65.175","url":null,"abstract":"Long term slow slip (LTSS) and non-volcanic low frequency earthquakes (LFEs) were reported in the central part of the Tokai district, central Japan. Such LTSS and LFE events are considered to take place at transition zone from stick-slip zone to stable sliding zone and to be associated with fluids on the subducting Philippine Sea plate’s surface. To clarify the spatial variation of the physical properties in this region, we estimated a three dimensional seismic attenuation structure using joint inversion method. In this study, we used 3688 spectra of 140 earthquakes which were observed by both temporary stations conducted from April to August in 2008 and permanent stations. Frequency band was divided equally among 24 between 0.78125 and 18.75 Hz and equally among 8 between 18.75 and 31.25 Hz. We gave Q blocks by dividing study area into 7 in the N-S direction between 137E and 138.5E degree, into 6 blocks in E-W direction between 34.5N and 35.7N, and 6 depth layers. We estimated frequency independent Q value of each block. In Q zone located along the Median tectonic line which divides the southwestern Japan into two parts; a old geologic belt and a new accretionary belt. In the lower crust of the land plate at the depths of 17 to 25km, a very high Q zone (about 2000) exists just above the region where large slip rate was observed in LTSS between 2001 and 2005. Since very few earthquakes occur in this high Q zone, that portion might consist of harder rocks than surroundings. On the contrary, the region just beneath the large slip zone has lower Q than surrounding area. Comparing our results with the seismic velocity structure derived from travel time tomography, we found the high Q zone approximately coincides with relatively high velocity zone, and lower Q zone corresponds to the relatively low velocity and high Vp/Vs region. As mentioned in previous studies, low Q zone with low velocity and high Vp/Vs is interpreted as the zone which involves high-pressure fluid. Probably the high Q zone above the large slip zone works as a cap rock and prevents the fluid moving toward the shallow part, then the fluid pressure becomes high and it affects the occurrence of slow slip in this region. Slow earthquakes called episodic tremor and slip (ETS) propagate over 100 kilometers at low velocities, ˜10 kilometers per day, along several plate interfaces. These low velocities differentiate slow earthquakes from ordinary earthquakes, and thus understanding their propagation processes is fundamental to understand the diversity and universality of earthquake processes. Com-prehensive modeling and previously-unreported correlations of migration patterns with energetics of tremor observed in Japan show that rheological fault heterogeneity essentially governs ETS propagations. The fault has persistent small-scale segmenta-tion, where the propagations always energetically started in brittle sections and decelerated in the ductile sections; spontaneous rupture calculations co","PeriodicalId":332254,"journal":{"name":"Journal of the Seismological Society of Japan","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114290763","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The source process of the 2011 off the Pacific coast of Tohoku Earthquake (Mw9.0) was complex and included multi sub-events. From the view of strong ground motion, there were two major peak waveforms observed around Tohoku district. These were caused by two major sub-events off Miyagi Prefecture near the epicenter. We divided each observed strong motion time history into two parts related to the two sub-events based on visual judgment. The inversion analysis was carried out to reveal high-frequency rupture areas using measured seismic intensity related to each sub-event as well as the whole event. We found that the first high-frequency rupture area was located near the hypocenter and extended northward. The second high-frequency rupture area had a substantial overlap with the first one and was nearer coastline of Miyagi Prefecture than the first, and its magnitude for seismic intensity is the same as the first. The result of the whole event shows that the high-frequency rupture areas consist two major parts. The north major part is related to two sub-events off Miyagi Prefecture. The south major part was located off-shore area near the north of Ibaraki Prefecture. Furthermore, we found that the first high-frequency rupture area was similar to that of the 1793 Kansei earthquake that was one of the major historical earthquakes in this region and the west of the high-frequency rupture area of the first two sub-events was overlapped with those of historical M7 class earthquakes off Miyagi Prefecture in 1861, 1897, 1936, 1978 and 2005 more or less. It shows that the events off Miyagi Prefecture do not be treated as simple characteristic earthquakes. We compared the high-frequency rupture areas with the source processes presented by researchers. At first, compared to the strong motion generation area (SMGA) models proposed by three research groups, our result is quite similar to the SMGAs of Kurahashi and Irikura (2011) in terms of rupture sequence and location. Secondly, the comparison with the rupture front process obtained from far-field P-waves using the back-projection method by Zhang et al. (2011) reveals that the three high-frequency rupture areas correspond to northward first rupture off Miyagi up to 60 seconds from origin, southwestward second rupture off Miyagi in next 40 seconds and southward third rupture from off-Fukushima to off-Ibaraki in final 40 seconds, respectively. Finally, compared to the source process obtained from joint inversion using near-field strong motion, teleseismic and geodetic data by Koketsu et al. (2011), we find that the first high-frequency rupture area corresponds to slowly expanded rupture process from the hypocenter, the second one corresponds to westward rupture with large slip from the trench accompanied with tsunami, and last one corresponds southward rupture up to off-shore of north Ibaraki Prefecture. The energy centroids of the second and last high-frequency rupture area are located at terminal rupture area of asperities
2011年太平洋沿岸东北地震(Mw9.0)的震源过程复杂，包含多个子事件。从强地面运动的角度来看，在东北地区观测到两个主要的峰值波形。这是由靠近震中的宫城县附近的两个主要次级事件引起的。我们根据视觉判断将每一个观测到的强运动时程分成与两个子事件相关的两个部分。利用与每个子事件和整个事件相关的测量地震烈度进行反演分析，以揭示高频破裂区域。发现第一高频破裂区位于震源附近，并向北延伸。第2次高频破裂区与第1次高频破裂区有大量重叠，且较第1次高频破裂区更靠近宫城县海岸线，地震烈度震级与第1次高频破裂区相同。整个事件的结果表明，高频破裂区由两个主要部分组成。北部主要部分与宫城县附近的两个子事件有关。南部主要部分位于茨城县北部附近的近海地区。第一次高频断裂带与该地区历史上主要地震之一的1793年感性地震的断裂带相似，前两次子事件的高频断裂带西部与1861年、1897年、1936年、1978年和2005年宫城县附近的历史M7级地震断裂带有一定的重叠。这表明宫城县外的地震不能被视为简单的特征地震。我们将高频破裂区与研究人员提出的震源过程进行了比较。首先，与三个研究组提出的强震发生区(SMGA)模型相比，我们的结果在破裂顺序和位置上与Kurahashi和Irikura(2011)的SMGA非常相似。其次，与Zhang等(2011)使用反投影法从远场纵波获得的破裂锋过程进行比较发现，三个高频破裂区分别对应于距离起点60秒的宫城向北的第一次破裂，距离起点40秒的宫城向西南的第二次破裂，以及距离起点40秒的从福岛外海到茨城外海向南的第三次破裂。最后，与Koketsu et al.(2011)利用近场强震、远震和大地测量数据联合反演得到的震源过程相比，我们发现第一个高频破裂区对应的是从震源开始缓慢扩展的破裂过程，第二个高频破裂区对应的是从海沟向西大滑动并伴有海啸的破裂，最后一个高频破裂区对应的是向南至茨城北近海的破裂。第二高频破裂区和最后高频破裂区的能量质心位于凸起的末端破裂区。我们在分析其他历史板块间事件时也发现了同样的特征[Takemura and Kanda(2008)]。
{"title":"High-frequency Rupture Areas during the 2011 Off the Pacific Coast of Tohoku Earthquake Inferred from Seismic Intensity Data","authors":"K. Kanda, M. Takemura, K. Hirotani, K. Ishikawa","doi":"10.4294/ZISIN.65.189","DOIUrl":"https://doi.org/10.4294/ZISIN.65.189","url":null,"abstract":"The source process of the 2011 off the Pacific coast of Tohoku Earthquake (Mw9.0) was complex and included multi sub-events. From the view of strong ground motion, there were two major peak waveforms observed around Tohoku district. These were caused by two major sub-events off Miyagi Prefecture near the epicenter. We divided each observed strong motion time history into two parts related to the two sub-events based on visual judgment. The inversion analysis was carried out to reveal high-frequency rupture areas using measured seismic intensity related to each sub-event as well as the whole event. We found that the first high-frequency rupture area was located near the hypocenter and extended northward. The second high-frequency rupture area had a substantial overlap with the first one and was nearer coastline of Miyagi Prefecture than the first, and its magnitude for seismic intensity is the same as the first. The result of the whole event shows that the high-frequency rupture areas consist two major parts. The north major part is related to two sub-events off Miyagi Prefecture. The south major part was located off-shore area near the north of Ibaraki Prefecture. Furthermore, we found that the first high-frequency rupture area was similar to that of the 1793 Kansei earthquake that was one of the major historical earthquakes in this region and the west of the high-frequency rupture area of the first two sub-events was overlapped with those of historical M7 class earthquakes off Miyagi Prefecture in 1861, 1897, 1936, 1978 and 2005 more or less. It shows that the events off Miyagi Prefecture do not be treated as simple characteristic earthquakes. We compared the high-frequency rupture areas with the source processes presented by researchers. At first, compared to the strong motion generation area (SMGA) models proposed by three research groups, our result is quite similar to the SMGAs of Kurahashi and Irikura (2011) in terms of rupture sequence and location. Secondly, the comparison with the rupture front process obtained from far-field P-waves using the back-projection method by Zhang et al. (2011) reveals that the three high-frequency rupture areas correspond to northward first rupture off Miyagi up to 60 seconds from origin, southwestward second rupture off Miyagi in next 40 seconds and southward third rupture from off-Fukushima to off-Ibaraki in final 40 seconds, respectively. Finally, compared to the source process obtained from joint inversion using near-field strong motion, teleseismic and geodetic data by Koketsu et al. (2011), we find that the first high-frequency rupture area corresponds to slowly expanded rupture process from the hypocenter, the second one corresponds to westward rupture with large slip from the trench accompanied with tsunami, and last one corresponds southward rupture up to off-shore of north Ibaraki Prefecture. The energy centroids of the second and last high-frequency rupture area are located at terminal rupture area of asperities","PeriodicalId":332254,"journal":{"name":"Journal of the Seismological Society of Japan","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127801002","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Japan Meteorological Agency has deployed strain-meters in Shizuoka, Aichi, and Nagano Prefectures, aiming to detect a slow slip phenomenon that is expected to occur just before the anticipated great earthquake of M8 class at the plate boundary. In this paper we propose a stacking method in which data at diff erent stations are added according to the following procedure. First, the observed waveform at each station is normalized by the noise level. Then, the normalized wave form is stacked one by one in the order of the magnitude of the signal to noise ratio, by reversing the polarity considering an assumed source location, if necessary, so as the signal to be all positive. This stacking procedure is stopped when the synthesized signal to noise ratio of the stacked waveform becomes the maximum. Members in the optimum data set that gives the largest signal to noise ratio become diff erent if the location of the assumed source is diff erent. It is shown that the signal to noise ratio of the stacked waveform obtained by this method is enhanced 2.3 times of that of the most favorable individual data. A slow slip event as small as Mw 5.0 would be detected if it occurs within the source area of the anticipated Tokai earthquake. We think the stacking method is applicable not only to the strain-meter data, but also to the GNSS and tilt-meter data and such an extension of the method may be eff ective to detect rising of magma beneath volcanoes.
{"title":"Development of Stacking Method for the Detection of Crustal Deformation","authors":"K. Miyaoka, T. Yokota","doi":"10.4294/ZISIN.65.205","DOIUrl":"https://doi.org/10.4294/ZISIN.65.205","url":null,"abstract":"The Japan Meteorological Agency has deployed strain-meters in Shizuoka, Aichi, and Nagano Prefectures, aiming to detect a slow slip phenomenon that is expected to occur just before the anticipated great earthquake of M8 class at the plate boundary. In this paper we propose a stacking method in which data at diff erent stations are added according to the following procedure. First, the observed waveform at each station is normalized by the noise level. Then, the normalized wave form is stacked one by one in the order of the magnitude of the signal to noise ratio, by reversing the polarity considering an assumed source location, if necessary, so as the signal to be all positive. This stacking procedure is stopped when the synthesized signal to noise ratio of the stacked waveform becomes the maximum. Members in the optimum data set that gives the largest signal to noise ratio become diff erent if the location of the assumed source is diff erent. It is shown that the signal to noise ratio of the stacked waveform obtained by this method is enhanced 2.3 times of that of the most favorable individual data. A slow slip event as small as Mw 5.0 would be detected if it occurs within the source area of the anticipated Tokai earthquake. We think the stacking method is applicable not only to the strain-meter data, but also to the GNSS and tilt-meter data and such an extension of the method may be eff ective to detect rising of magma beneath volcanoes.","PeriodicalId":332254,"journal":{"name":"Journal of the Seismological Society of Japan","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128451568","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"強震動の継続時間から見た平成15年（2003年）十勝沖地震とその最大余震の破壊伝播特性","authors":"重樹 青木, 康宏 吉田, 明男 勝間田, 充之 干場","doi":"10.4294/ZISIN.65.163","DOIUrl":"https://doi.org/10.4294/ZISIN.65.163","url":null,"abstract":"","PeriodicalId":332254,"journal":{"name":"Journal of the Seismological Society of Japan","volume":"158 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124427581","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"特集：2011年東北地方太平洋沖地震（第3部）","authors":"徳仁 海野","doi":"10.4294/ZISIN.65.43","DOIUrl":"https://doi.org/10.4294/ZISIN.65.43","url":null,"abstract":"","PeriodicalId":332254,"journal":{"name":"Journal of the Seismological Society of Japan","volume":"44 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124452976","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"2011年（平成23年）東北地方太平洋沖地震に伴う地震時および地震後の地殻変動と断層モデル","authors":"尚 水藤, 卓也 西村, 知勝 小林, 小沢 慎三郎, 幹男 飛田, 哲郎 今給黎","doi":"10.4294/ZISIN.65.95","DOIUrl":"https://doi.org/10.4294/ZISIN.65.95","url":null,"abstract":"","PeriodicalId":332254,"journal":{"name":"Journal of the Seismological Society of Japan","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122264106","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"2011年4月11日福島県浜通りの地震（Mj7.0）の震源過程","authors":"和人 引間","doi":"10.4294/ZISIN.64.243","DOIUrl":"https://doi.org/10.4294/ZISIN.64.243","url":null,"abstract":"","PeriodicalId":332254,"journal":{"name":"Journal of the Seismological Society of Japan","volume":"73 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131614390","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
H. Kimura, H. Horikawa, M. Suehiro, Yasuhiko Akinaga
We conducted an S-wave shallow seismic reflection profiling to reveal subsurface structure deformed by a blind thrust across the Ayasegawa fault in the northern area of the Omiya upland, central Japan. The NW-SE trending and SW dipping Ayasegawa fault is located in the southeastern part of the Kanto-heiya-hokuseien fault zone along the northwestern margin of the Kanto Plain, and is one of the nearest active faults to the Tokyo metropolitan area. This seismic profiling consisted of two survey lines which are Line 1 with a length of about 0.5km and Line 2 with that of about 0.9km. An automated S-wave plank hammering system (Hanshin Consultants Co., Ltd.) was used as seismic source. Both the standard shot intervals and group intervals of geophones were 2m. The common mid-point seismic reflection data was acquired by a digital telemetry recording system (JGI, Inc.). Folded strata, which were showing the deformation zone, were clearly recognized in the obtained post-stack migrated, depth converted seismic section. The width of the deformation zone with anticlinal uplift is about 0.8km along the seismic section. The relative uplift rate in the southwestern side of the Ayasegawa fault is 0.12-0.14mm/yr at the crest of the anticlinal uplift inside the deformation zone, and is 0.08-0.09mm/yr outside the deformation zone.
{"title":"S-wave Seismic Reflection Profiling in the Northern Area of the Omiya Upland: Uplift Rate during Late Quaternary Raised by the Ayasegawa Fault in the Kanto-heiya-hokuseien (Northwestern Margin of the Kanto Plain) Fault Zone, Central Japan","authors":"H. Kimura, H. Horikawa, M. Suehiro, Yasuhiko Akinaga","doi":"10.4294/ZISIN.64.117","DOIUrl":"https://doi.org/10.4294/ZISIN.64.117","url":null,"abstract":"We conducted an S-wave shallow seismic reflection profiling to reveal subsurface structure deformed by a blind thrust across the Ayasegawa fault in the northern area of the Omiya upland, central Japan. The NW-SE trending and SW dipping Ayasegawa fault is located in the southeastern part of the Kanto-heiya-hokuseien fault zone along the northwestern margin of the Kanto Plain, and is one of the nearest active faults to the Tokyo metropolitan area. This seismic profiling consisted of two survey lines which are Line 1 with a length of about 0.5km and Line 2 with that of about 0.9km. An automated S-wave plank hammering system (Hanshin Consultants Co., Ltd.) was used as seismic source. Both the standard shot intervals and group intervals of geophones were 2m. The common mid-point seismic reflection data was acquired by a digital telemetry recording system (JGI, Inc.). Folded strata, which were showing the deformation zone, were clearly recognized in the obtained post-stack migrated, depth converted seismic section. The width of the deformation zone with anticlinal uplift is about 0.8km along the seismic section. The relative uplift rate in the southwestern side of the Ayasegawa fault is 0.12-0.14mm/yr at the crest of the anticlinal uplift inside the deformation zone, and is 0.08-0.09mm/yr outside the deformation zone.","PeriodicalId":332254,"journal":{"name":"Journal of the Seismological Society of Japan","volume":"69 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129300041","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Harada, T. Aketagawa, Hiroshi Itô, R. Honda, Y. Yukutake, K. Itadera, A. Yoshida
We investigated the spatial distribution, temporal change and some statistical features of the swarm activity in Hakone volcano after the 2011 Off the Pacific Coast of Tohoku earthquake (hereafter, the 2011 Tohoku earthquake). Though overall spatial distribution of the activity was not much different from that observed at swarm activities in recent years, its temporal change was quite different: Contrary to recent activities in which burst-like earthquake occurrence was observed repeatedly, the activity after the 2011 Tohoku earthquake declined rather rapidly and monotonously according to an inverse power law of the elapsed time from the 2011 Tohoku earthquake. This feature was most clearly seen in the change of daily number of earthquake clusters. Another notable feature of the activity was that the b value was significantly smaller than the values of recent swarm activities. These characteristics suggest that the swarm activity was induced by the sudden increase of static stress caused by the 2011 Tohoku earthquake on March 11.
{"title":"Swarm Activity in Hakone Volcano Induced by the 2011 Off the Pacific Coast of Tohoku Earthquake","authors":"M. Harada, T. Aketagawa, Hiroshi Itô, R. Honda, Y. Yukutake, K. Itadera, A. Yoshida","doi":"10.4294/ZISIN.64.135","DOIUrl":"https://doi.org/10.4294/ZISIN.64.135","url":null,"abstract":"We investigated the spatial distribution, temporal change and some statistical features of the swarm activity in Hakone volcano after the 2011 Off the Pacific Coast of Tohoku earthquake (hereafter, the 2011 Tohoku earthquake). Though overall spatial distribution of the activity was not much different from that observed at swarm activities in recent years, its temporal change was quite different: Contrary to recent activities in which burst-like earthquake occurrence was observed repeatedly, the activity after the 2011 Tohoku earthquake declined rather rapidly and monotonously according to an inverse power law of the elapsed time from the 2011 Tohoku earthquake. This feature was most clearly seen in the change of daily number of earthquake clusters. Another notable feature of the activity was that the b value was significantly smaller than the values of recent swarm activities. These characteristics suggest that the swarm activity was induced by the sudden increase of static stress caused by the 2011 Tohoku earthquake on March 11.","PeriodicalId":332254,"journal":{"name":"Journal of the Seismological Society of Japan","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127063986","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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