Listening to a sound representing ground motion is valuable to understand an earthquake intuitively compared with only seeing a waveform. In this paper, we propose a new method to make a sound of earthquake, in which several rules different from existing methods are used. In our new method, a sound of earthquake is generated by modifying the frequency information of generating function based on the theory of symmetric Fourier analysis. Applying the method to the JMA Kobe seismogram in 1995 South Hyogo Prefecture Earthquake and predicted waveform at Sannomaru, Nagoya, in future Tokai and Tonankai earthquake, three features of the sound generated by this method are confirmed: the sound has same duration time as the seismogram, high sound is heard when the seismogram has high frequency, and loud sound is heard when the seismogram has large amplitude.
{"title":"Synthesis Method of Sound Which Has Same Duration Time as a Seismogram","authors":"T. Hirai, N. Fukuwa","doi":"10.4294/ZISIN.63.153","DOIUrl":"https://doi.org/10.4294/ZISIN.63.153","url":null,"abstract":"Listening to a sound representing ground motion is valuable to understand an earthquake intuitively compared with only seeing a waveform. In this paper, we propose a new method to make a sound of earthquake, in which several rules different from existing methods are used. In our new method, a sound of earthquake is generated by modifying the frequency information of generating function based on the theory of symmetric Fourier analysis. Applying the method to the JMA Kobe seismogram in 1995 South Hyogo Prefecture Earthquake and predicted waveform at Sannomaru, Nagoya, in future Tokai and Tonankai earthquake, three features of the sound generated by this method are confirmed: the sound has same duration time as the seismogram, high sound is heard when the seismogram has high frequency, and loud sound is heard when the seismogram has large amplitude.","PeriodicalId":332254,"journal":{"name":"Journal of the Seismological Society of Japan","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134547860","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}
Takeshi Nakamura, H. Takenaka, T. Okamoto, Y. Kaneda
{"title":"A Study of the Finite Difference Solution for 3D Seismic Wavefields near a Fluid-Solid Interface","authors":"Takeshi Nakamura, H. Takenaka, T. Okamoto, Y. Kaneda","doi":"10.4294/ZISIN.63.189","DOIUrl":"https://doi.org/10.4294/ZISIN.63.189","url":null,"abstract":"","PeriodicalId":332254,"journal":{"name":"Journal of the Seismological Society of Japan","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116781500","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}
We developed a comprehensive statistical validation system of crustal activities with which to easily address spatially and temporally sufficient range of a database of geophysical measures. The system involves carrying out the following four processes: (1) creating the database of geophysical measures with spatially and temporally gridded and other convenient formats, (2) comparing any two geophysical measures, at least one of which is time-variable, (3) classifying the spatiotemporal relationship of these geophysical measures into some types by defining a statistical index, and (4) evaluating and validating the relationships between classification results and the occurrence of target physical events such as large inland earthquakes. With the system, we aim for making a statistical model, or an appropriate rule for monitoring of crustal activities. Formulation of the rule is, in turn, expected to lead to comprehensive understanding of crustal activities. Here, we focused on the relations of seismicity and strain rate to introduce the conception and algorithm of the system. The system requires input of the database and other parameters and leads to output of various spatiotemporal distributions, 2-by-2 contingency tables, and probability gains for prediction and alarm rates for target physical events.
{"title":"Understanding of Crustal Activity with Statistical Approaches","authors":"M. Kawamura, T. Kudo, K. Yamaoka, M. Furumoto","doi":"10.4294/ZISIN.63.123","DOIUrl":"https://doi.org/10.4294/ZISIN.63.123","url":null,"abstract":"We developed a comprehensive statistical validation system of crustal activities with which to easily address spatially and temporally sufficient range of a database of geophysical measures. The system involves carrying out the following four processes: (1) creating the database of geophysical measures with spatially and temporally gridded and other convenient formats, (2) comparing any two geophysical measures, at least one of which is time-variable, (3) classifying the spatiotemporal relationship of these geophysical measures into some types by defining a statistical index, and (4) evaluating and validating the relationships between classification results and the occurrence of target physical events such as large inland earthquakes. With the system, we aim for making a statistical model, or an appropriate rule for monitoring of crustal activities. Formulation of the rule is, in turn, expected to lead to comprehensive understanding of crustal activities. Here, we focused on the relations of seismicity and strain rate to introduce the conception and algorithm of the system. The system requires input of the database and other parameters and leads to output of various spatiotemporal distributions, 2-by-2 contingency tables, and probability gains for prediction and alarm rates for target physical events.","PeriodicalId":332254,"journal":{"name":"Journal of the Seismological Society of Japan","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117272545","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":"Statistical Detection of Change in the Distributions of Focal Mechanism Type on Triangle Diagram","authors":"S. Aoki, M. Okada","doi":"10.4294/ZISIN.63.101","DOIUrl":"https://doi.org/10.4294/ZISIN.63.101","url":null,"abstract":"","PeriodicalId":332254,"journal":{"name":"Journal of the Seismological Society of Japan","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123615983","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}
Changes of the seismicity pattern were examined in the Tokai and the Tonankai seismogenic regions and discussed with respect to possible crustal movements. Temporal transitions of the seismicity pattern were followed by calculating correlation coefficients between two spatial distribu.tions of earthquakes for the period of interest. I sampled M 3.5 and greater earthquakes from the JMA catalog. The catalog contains a problem of non-uniform observations, however the method utilized here is insensitive to this. Following the changes represented in the correlation coefficients, I found that the recent seismicity pattern is approaching the reference, which is precisely the pattern preceding the 1944 Tonankai earthquake. The tendency is common to both the Tokai and Tonankai regions. This implies that a similar crustal movement reappeared after a long hiatus of about sixty years in both regions. One possible cause of common changes in the Tokai and Tonankai regions is the long-term slow slip beneath Lake Hamana that has progressed during the last decade. If the cause of the recent changes in the seismicity pattern is attributed to this slow slip, the same slow slip can be interpreted as having progressed beneath Lake Hamana before the Tonankai event, which created a characteristic seismicity pattern in the past.
{"title":"Reappearance of Characteristic Seismicity Pattern in the Tokai and Tonankai Regions (Seismic Activity Change in the Tokai Region: Part 6)","authors":"S. Matsumura","doi":"10.4294/ZISIN.63.83","DOIUrl":"https://doi.org/10.4294/ZISIN.63.83","url":null,"abstract":"Changes of the seismicity pattern were examined in the Tokai and the Tonankai seismogenic regions and discussed with respect to possible crustal movements. Temporal transitions of the seismicity pattern were followed by calculating correlation coefficients between two spatial distribu.tions of earthquakes for the period of interest. I sampled M 3.5 and greater earthquakes from the JMA catalog. The catalog contains a problem of non-uniform observations, however the method utilized here is insensitive to this. Following the changes represented in the correlation coefficients, I found that the recent seismicity pattern is approaching the reference, which is precisely the pattern preceding the 1944 Tonankai earthquake. The tendency is common to both the Tokai and Tonankai regions. This implies that a similar crustal movement reappeared after a long hiatus of about sixty years in both regions. One possible cause of common changes in the Tokai and Tonankai regions is the long-term slow slip beneath Lake Hamana that has progressed during the last decade. If the cause of the recent changes in the seismicity pattern is attributed to this slow slip, the same slow slip can be interpreted as having progressed beneath Lake Hamana before the Tonankai event, which created a characteristic seismicity pattern in the past.","PeriodicalId":332254,"journal":{"name":"Journal of the Seismological Society of Japan","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127472666","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}
Along the Nanakai-Suruga trough, where the Philippine Sea plate is being subducted beneath southwest Japan, nine series of great Tokai and Nankai earthquakes have recurred every 100 200 years during historical times since 684 A.D., and brought about significant tsunamis. Recently, geologists investigated tsunami deposits in the Ryujin-ike lagoon in Oita Prefecture and found 40 sand layers during the past 3,300 years including eight remarkable thick layers. They inferred that the uppermost three thick layers had been deposited by large tsunamis due to the “giant Nankai earthquakes” in 684, 1361, and 1707 A.D. which ruptured the Tokai and Nankai source regions simultaneously, and that “giant Nankai earthquakes” had recurred every about 450 years. In order to examine these inferences, we carried out numerical tsunami simulation at the Ryujin-ike lagoon assuming various static fault models based on existing models of the 1707 Ho’ei, 1854 Ansei-Nankai, and 1946 Showa-Nankai earthquakes. As the results, it has been revealed that the tsunami waveform and its maximum height near the Ryujin-ike lagoon depend strongly on the southwesternmost fault slip of the “giant Nankai earthquake” and insensitive to faulting in the Tokai region. Therefore, we conclude that the large tsunamis near the Ryujin-ike lagoon suggested by thick tsunami deposits cannot show the occurrence of “giant Nankai earthquakes” which ruptured the Tokai and Nankai sources simultaneously. Moreover, for a large tsunami near the Ryujin-ike lagoon, the location and the slip amount of the southwesternmost fault plane of the Nankai earthquake have a trade-o# relationship between each other, which makes it impossible to infer correctly the causal fault of the large tsunami by means of the Ryujin-ike data alone. In addition, there is disagreement between the “giant Nankai earthquakes” inferred by the thick sand layers in the Ryujin-ike lagoon and those inferred by the study of historiographical seismology. In conclusion, the eight remarkable sand layers in the Ryujin-ike lagoon cannot be regarded as the traces of the “giant Nankai earthquakes.”
{"title":"Examination of “Giant Nankai, Japan, Earthquakes” Suggested by Tsunami Deposits in the Ryujin-ike Lagoon in Oita Prefecture, Kyushu, by Means of Tsunami Simulation","authors":"T. Harada, K. Ishibashi","doi":"10.4294/ZISIN.63.71","DOIUrl":"https://doi.org/10.4294/ZISIN.63.71","url":null,"abstract":"Along the Nanakai-Suruga trough, where the Philippine Sea plate is being subducted beneath southwest Japan, nine series of great Tokai and Nankai earthquakes have recurred every 100 200 years during historical times since 684 A.D., and brought about significant tsunamis. Recently, geologists investigated tsunami deposits in the Ryujin-ike lagoon in Oita Prefecture and found 40 sand layers during the past 3,300 years including eight remarkable thick layers. They inferred that the uppermost three thick layers had been deposited by large tsunamis due to the “giant Nankai earthquakes” in 684, 1361, and 1707 A.D. which ruptured the Tokai and Nankai source regions simultaneously, and that “giant Nankai earthquakes” had recurred every about 450 years. In order to examine these inferences, we carried out numerical tsunami simulation at the Ryujin-ike lagoon assuming various static fault models based on existing models of the 1707 Ho’ei, 1854 Ansei-Nankai, and 1946 Showa-Nankai earthquakes. As the results, it has been revealed that the tsunami waveform and its maximum height near the Ryujin-ike lagoon depend strongly on the southwesternmost fault slip of the “giant Nankai earthquake” and insensitive to faulting in the Tokai region. Therefore, we conclude that the large tsunamis near the Ryujin-ike lagoon suggested by thick tsunami deposits cannot show the occurrence of “giant Nankai earthquakes” which ruptured the Tokai and Nankai sources simultaneously. Moreover, for a large tsunami near the Ryujin-ike lagoon, the location and the slip amount of the southwesternmost fault plane of the Nankai earthquake have a trade-o# relationship between each other, which makes it impossible to infer correctly the causal fault of the large tsunami by means of the Ryujin-ike data alone. In addition, there is disagreement between the “giant Nankai earthquakes” inferred by the thick sand layers in the Ryujin-ike lagoon and those inferred by the study of historiographical seismology. In conclusion, the eight remarkable sand layers in the Ryujin-ike lagoon cannot be regarded as the traces of the “giant Nankai earthquakes.”","PeriodicalId":332254,"journal":{"name":"Journal of the Seismological Society of Japan","volume":"62 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124572212","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}
Since variations of slip on plate boundaries depend on frictional properties, it is essential to know frictional parameters on the fault, as well as initial values of simulation variables for earthquake generation prediction. In this study, an adjoint data assimilation method is introduced to a simpli.ed fault model with a rate-and state-dependent friction law as a .rst step toward the goal of estimating the frictional parameters and initial values of simulation variables in a realistic situation. The method is applied to the simpli.ed model which mimics the 2003 Tokachi-oki afterslip. We make synthetic data set, slip velocities on the fault surface by assigning the “true” frictional parameters and initial values artificially. We investigate the feasibility of estimating frictional parameters and initial values through the adjoint data assimilation method on the assumption of knowing “background” values and observations. It is confirmed that the adjoint data assimilation method is computationally efficient to estimate control variables such as frictional parameters and initial values by time-trajectory fitting of observation data, compared to the grid search method. Also, we examine the sensitivity of each frictional parameter and initial value to the observed afterslip velocity data. In the range of our search using afterslip data, we .nd that 1) the initial value of velocity can be constrained, 2) the initial value of state variable cannot be constrained, 3) the frictional parameter value of a-b is well retrieved in the region where aftreslip velocity is observed, and 4) the value of characteristic length L can be retrieved only from the early portion of afterslip velocity data, where the velocity is rapidly changing.
{"title":"Estimation of Frictional Parameters and Initial Values of Simulation Variables Using an Adjoint Data Assimilation Method with Synthetic Afterslip Data","authors":"M. Kano, S. Miyazaki, Kosuke Ito, K. Hirahara","doi":"10.4294/ZISIN.63.57","DOIUrl":"https://doi.org/10.4294/ZISIN.63.57","url":null,"abstract":"Since variations of slip on plate boundaries depend on frictional properties, it is essential to know frictional parameters on the fault, as well as initial values of simulation variables for earthquake generation prediction. In this study, an adjoint data assimilation method is introduced to a simpli.ed fault model with a rate-and state-dependent friction law as a .rst step toward the goal of estimating the frictional parameters and initial values of simulation variables in a realistic situation. The method is applied to the simpli.ed model which mimics the 2003 Tokachi-oki afterslip. We make synthetic data set, slip velocities on the fault surface by assigning the “true” frictional parameters and initial values artificially. We investigate the feasibility of estimating frictional parameters and initial values through the adjoint data assimilation method on the assumption of knowing “background” values and observations. It is confirmed that the adjoint data assimilation method is computationally efficient to estimate control variables such as frictional parameters and initial values by time-trajectory fitting of observation data, compared to the grid search method. Also, we examine the sensitivity of each frictional parameter and initial value to the observed afterslip velocity data. In the range of our search using afterslip data, we .nd that 1) the initial value of velocity can be constrained, 2) the initial value of state variable cannot be constrained, 3) the frictional parameter value of a-b is well retrieved in the region where aftreslip velocity is observed, and 4) the value of characteristic length L can be retrieved only from the early portion of afterslip velocity data, where the velocity is rapidly changing.","PeriodicalId":332254,"journal":{"name":"Journal of the Seismological Society of Japan","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133684827","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":"A Small Scale Long-term Slow Slip Occurred in the Western Shikoku in 2005","authors":"A. Kobayashi","doi":"10.4294/ZISIN.63.97","DOIUrl":"https://doi.org/10.4294/ZISIN.63.97","url":null,"abstract":"","PeriodicalId":332254,"journal":{"name":"Journal of the Seismological Society of Japan","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115589768","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 Philippine Sea plate has subducted beneath southwest Japan at the Nankai Trough, causing megathrust earthquakes every 100-140 years. The subduction process shows lateral variations along the trough, such as a bending of the plate interface beneath the Kii Peninsula and rapid changes of strike and dip off the east coast of Kyushu. We invert three-dimensional GPS velocities using ABIC geodetic inversion technique to estimate interseismic slip de.cit distribution at the Nankai Trough. The studied area is roughly from Kii peninsula to eastern Kyushu (131.5-137E, 31-35N). In the ABIC geodetic inversion some initial constraints are needed to stabilize solutions, such that the slip at the outer margin of the fault is set to zero. For the estimation of interseismic slip de.cit on the plate interface, however, these constraints are unrealistic because slip de.cit distribution continues later.ally to the outside of the target area. In this study we propose a repeated inversion method that shifts target area laterally along the plate boundary. This method averages slip de.cit estimates at the same point obtained from more than three consecutive inversions. The estimates obtained near the lateral margin, which may be strongly affected by the non-slip constraints at the outer margin, are excluded from the averaging. As a result final solutions are stabilized regardless the setting of the region. The final slip de.cit distribution at the Nankai Trough shows high contrast of strong and weak plate locking zones. Down-dip variation of the slip de.cit is emphasized more clearly but the lateral variation becomes moderate compared with the single inversion result.
{"title":"Spatial Variation of Slip Deficit Rate at the Nankai Trough, Southwest Japan Inferred from Three-Dimensional GPS Crustal Velocity Fields","authors":"S. Ichitani, Kentaro Tsuka, T. Tabei","doi":"10.4294/ZISIN.63.35","DOIUrl":"https://doi.org/10.4294/ZISIN.63.35","url":null,"abstract":"The Philippine Sea plate has subducted beneath southwest Japan at the Nankai Trough, causing megathrust earthquakes every 100-140 years. The subduction process shows lateral variations along the trough, such as a bending of the plate interface beneath the Kii Peninsula and rapid changes of strike and dip off the east coast of Kyushu. We invert three-dimensional GPS velocities using ABIC geodetic inversion technique to estimate interseismic slip de.cit distribution at the Nankai Trough. The studied area is roughly from Kii peninsula to eastern Kyushu (131.5-137E, 31-35N). In the ABIC geodetic inversion some initial constraints are needed to stabilize solutions, such that the slip at the outer margin of the fault is set to zero. For the estimation of interseismic slip de.cit on the plate interface, however, these constraints are unrealistic because slip de.cit distribution continues later.ally to the outside of the target area. In this study we propose a repeated inversion method that shifts target area laterally along the plate boundary. This method averages slip de.cit estimates at the same point obtained from more than three consecutive inversions. The estimates obtained near the lateral margin, which may be strongly affected by the non-slip constraints at the outer margin, are excluded from the averaging. As a result final solutions are stabilized regardless the setting of the region. The final slip de.cit distribution at the Nankai Trough shows high contrast of strong and weak plate locking zones. Down-dip variation of the slip de.cit is emphasized more clearly but the lateral variation becomes moderate compared with the single inversion result.","PeriodicalId":332254,"journal":{"name":"Journal of the Seismological Society of Japan","volume":"122 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117311029","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}
Toshiyuki Tanaka, H. Aoki, Masayoshi Tajikara, Mio Shimoyama, K. Nozaki, A. Yamamoto
The Tegano fault is an active fault, which is important from the perspective of the evolutionary process of reverse faults and for earthquake disaster prevention. It is believed that the longer and older Byobusan fault, which runs side by side with the Tegano fault, affects the formation of the Tegano fault. We performed precise gravity measurements to study the origin of the fault. Then, we estimated the basement structure in conjunction with a preexisting shallow re.ection survey as the constraining condition. By adopting differential filtering, we were able to see that the dip angle of the Tegano fault is low, whereas the angle of the Byobusan fault is high. The inferred schematic pro.le of the Tegano fault is consistent with a preexisting theory of the evolution of a reverse fault; this supports the hypothesis that the Tegano fault was derived from the deep part of the Byobusan fault. Moreover, we found that most of the fault plane of the Tegano fault is shallower than 1 km below the surface. Although the tectonic landform in the Tegano fault is young (or, the Byobusan fault is old), the deep part of the Tegano fault or the Byobusan fault may be capable of producing an earthquake. When assessing an active fault, it is important to comprehensively consider not only geomorphologic and ser.cial-geologic surveys but also gravimetrical ones.
{"title":"Basement Structure in and around the Tegano Fault, Central Japan","authors":"Toshiyuki Tanaka, H. Aoki, Masayoshi Tajikara, Mio Shimoyama, K. Nozaki, A. Yamamoto","doi":"10.4294/ZISIN.63.11","DOIUrl":"https://doi.org/10.4294/ZISIN.63.11","url":null,"abstract":"The Tegano fault is an active fault, which is important from the perspective of the evolutionary process of reverse faults and for earthquake disaster prevention. It is believed that the longer and older Byobusan fault, which runs side by side with the Tegano fault, affects the formation of the Tegano fault. We performed precise gravity measurements to study the origin of the fault. Then, we estimated the basement structure in conjunction with a preexisting shallow re.ection survey as the constraining condition. By adopting differential filtering, we were able to see that the dip angle of the Tegano fault is low, whereas the angle of the Byobusan fault is high. The inferred schematic pro.le of the Tegano fault is consistent with a preexisting theory of the evolution of a reverse fault; this supports the hypothesis that the Tegano fault was derived from the deep part of the Byobusan fault. Moreover, we found that most of the fault plane of the Tegano fault is shallower than 1 km below the surface. Although the tectonic landform in the Tegano fault is young (or, the Byobusan fault is old), the deep part of the Tegano fault or the Byobusan fault may be capable of producing an earthquake. When assessing an active fault, it is important to comprehensively consider not only geomorphologic and ser.cial-geologic surveys but also gravimetrical ones.","PeriodicalId":332254,"journal":{"name":"Journal of the Seismological Society of Japan","volume":"45 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130319122","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：