著者

勝間田 明男

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.53, no.1, pp.83-88, 2000-07-25 (Released:2010-03-11)

参考文献数

20

著者

石橋 克彦

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.28, no.3, pp.347-364, 1975-10-10 (Released:2010-03-11)

参考文献数

31

被引用文献数

1

---

For the purpose of precise relocation of earthquakes which had occurred in Japan around the first quarter of this century, a computer program was written which calculates hypocenter parameters by the method of least squares using S-P times at more than three stations and employing an arbitrary multi-layered crustal structure.As examples of relocation, about five semi-destructive earthquakes in the Kanto district: the Ryugasaki earthquake of 1921, the Yatabe earthquake of 1922, the Mitsukaido earthquake of 1923, the Uraga Channel earthquake of 1922 and the Haneda earthquake of 1926, all near-field S-P time data were carefully examined and hypocenters were redetermined. The epicenters and the focal depths obtained are expected to be uncertain by less than ±10km except the Uraga Channel earthquake. The former three, which has been suspected to be precursory activities of the Great Kanto earthquake of 1923, were ascertained to have their origins in the upper mantle beneath the SW part of the Ibaraki Prefecture where is even now a remarkable swarm area.

著者

加納 靖之

出版者

日本地震学会

雑誌

地震. 2輯 (ISSN:00371114)

巻号頁・発行日

vol.70, pp.171-182, 2017-11

---

It has long been believed that a M6.1 earthquake occurred on November 14, 1831 in Saga, southwest Japan. The event relies on a single entry from note of “Tenpo Zakki", which is a collection of miscellaneous notes between 1831 and 1844. Here we propose that the location for the earthquake is likely misinterpreted. Reexamination of the note shows that the earthquake occurred on November 13, 1831, as was recognized in 1919. The original location was thought to be in Saga because according to the note the earthquake was reported from “Hizen-no-kami” (lord of Saga). Analyses of the time it took for the news to reach Edo (Tokyo) show that the location of the earthquake is possibly not Saga, but Aizu, in northeast Japan. The note of “Tenpo Zakki” shows that the information of the event reached Edo in 5 days. However, it was impossible to deliver a letter from Saga to Edo in 5 days at that time. No description on the earthquake was found in diaries written around Saga.“Tenpo Zakki”might have mistaken“Higo-no-kami”(lord of Aizu) for “Hizen-no-kami".This result contributes to improvement of the list of historical earthquakes for Japan.

著者

功刀 卓 青井 真 中村 洋光 藤原 広行 森川 信之

出版者

SEISMOLOGICAL SOCIETY OF JAPAN

雑誌

地震 第1輯 (ISSN:00371114)

巻号頁・発行日

vol.60, no.4, pp.243-252, 2008

被引用文献数

20

---

A new calculation method is proposed for a real-time seismic intensity indicator (<i>I</i>_r), whose concept is similarly to the JMA seismic intensity (<i>I</i>_JMA)defined by Japan Meteorological Agency. With the increasing requirements of earthquake early warning (EEW) system, it is much more obvious that <i>I</i>_JMA has a real-time delay since the <i>I</i>_JMA needs a filtering operation in frequency domain. In order to improve the real-time calculation suitable for the EEW system, a new real-time seismic intensity indicator, <i>I</i>_r (real-time seismic intensity), is defined by using an approximating filter in time domain instead of the original filter in frequency domain. This indicator, <i>I</i>_r,can be calculated as a time series on real-time and its maximum value, <i>I</i>_a (approximate seismic intensity), corresponds to an approximate value of <i>I</i>_JMA. The relationships between <i>I</i>_JMA and <i>I</i>_a value are examined by means of using a large number of strong motion records. Results show that <i>I</i>_a value estimates <i>I</i>_JMA with reasonable accuracy in wide intensity ranges. For a small computing system like a strong-motion seismograph, it is easier to process <i>I</i>_r than processing <i>I</i>_JMA. Therefore, <i>I</i>_r is suitable for using in an EEW system based on the concept of JMA seismic intensity.

著者

宮部 直巳

出版者

公益社団法人 日本地震学会

雑誌

地震 第1輯 (ISSN:00371114)

巻号頁・発行日

vol.9, no.1, pp.6-14_1, 1937-01-15 (Released:2010-03-09)

著者

堀内 茂木 山本 明 松沢 暢 河野 俊夫 長谷川 昭 高木 章雄 伊神 輝 山田 守 青木 治三

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.38, no.4, pp.529-539, 1985-12-25 (Released:2010-03-11)

参考文献数

11

被引用文献数

1

---

A real-time system of automatic detection and location of seismic events has been developed by using a personal computer. Since speed of computation by a personal computer is low, a simple digital band-pass filter has been developed for the real-time system. The band-pass filter needs only several times of addition and subtraction to get an output. Event dection is based on a ratio of short to long term average of outputs of the filter whose cutoff frequencies are set to decrease amplitude of long period noise owing to microtremor and amplitude of short period noise owing to culture. Arrival times of the P and S waves are determined by applying Akaike Information Criterion (AIC) to outputs of the band-pass filter with narrow band whose central frequency is set to be a value of predominant frequency of the seismic signal.A temporary seismic observation with 8 stations for the aftershocks of the 1984 Western Nagano Prefecture Earthquake has been made by the use of radio and telephone telemetries. The real-time system of the automatic location of the seismic events was tested to demonstrate that hypocenter distribution obtained by the real-time system is nearly consistent with that determined from arrival time data which were read manually. It is shown that hypocenters of 60% among triggered events can be determined by this real-time system.

著者

植平 賢司 深畑 幸俊 飯高 隆 溝上 恵

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.47, no.3, pp.347-350, 1994-10-14 (Released:2010-03-11)

参考文献数

4

著者

溜渕 功史 山田 安之 石垣 祐三 高木 康伸 中村 雅基 前田 憲二 岡田 正実

出版者

SEISMOLOGICAL SOCIETY OF JAPAN

雑誌

地震 第1輯 (ISSN:00371114)

巻号頁・発行日

vol.62, no.4, pp.193-207, 2010

---

We found eight <I>M</I> 5.1 characteristic earthquakes regularly occurring since 1966 on the plate boundary between the Eurasian plate and the Philippine Sea plate near Miyakojima Island, the Ryukyu Arc, Japan. The quake recurrence interval was 5.89 years in average, and the standard deviation was only 0.73 years. The accumulating stress presumably ruptured the same asperity enclosed by the creeping zone repeatedly. Also, we found three other groups of small repeating earthquakes of <I>M</I> 4, which occurred close to the hypocenters of the <I>M</I> 5 events. Those groups also occurred regularly and we can consider them to be 'characteristic' earthquake sequences. Now, we called those groups A, B, and C. It is not clear whether groups A and B had an intrinsic recurrence interval or if they influenced each other. However, two events of group C occurred within one week after the <I>M</I> 5 quakes, indicating that the <I>M</I> 5 events triggered the group C events whose asperity had suffcient strain energy. No earthquake exceeding <I>M</I> 7, which could change the recurrence intervals, has been observed on the subduction zone around the Ryukyu Islands. Therefore, there should be numerous characteristic earthquake sequences in other areas of the Ryukyu district. We expect that the next <I>M</I> 5 earthquake at 50 km depth on the plate boundary near Miyakojima Island will occur between September 2012 and July 2014 with 70% probability, using the small-sample theory with a log-normal distribution model. Moreover, the <I>M</I> 5 event may be accompanied by an <I>M</I> 4 quake that could rupture the asperity of group C within one week.

著者

諸井 孝文 武村 雅之

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.52, no.1, pp.11-24, 1999-06-30 (Released:2010-03-11)

参考文献数

37

被引用文献数

1 7

---

The distribution of seismic intensity I=VII (very disastrous) for the 1995 Hyogoken-Nanbu earthquake was reported by the Japan Meteorological Agency (JMA). It was the first announcement since the seismic intensity in JMA scale had been revised in 1949 to include the highest class of I=VII. Originally the seismic intensity of I=VII was defined as “strong ground motion with collapse more than 30% of wooden houses”, which was based on destructive damage at the 1948 Fukui earthquake. During the last half century, aseismic design of wooden houses has progressed especially due to the popularization of the standard building code published in 1950. Recent cities like Kobe include various kinds of buildings in seismic performance from modern earthquake-resisting structures to old and vulnerable residences. Therefore the seismic intensity of I=VII should be recognized as “with collapse more than 30% of less aseismic wooden houses such as those built before 1950”. From these points, it must be confirmed whether the increase of the seismic performance of buildings was taken into account in the reported distribution of I=VII. First we review the term of “collapse of houses”. Then relationship between the collapse rate of houses and the overturning acceleration of tombstones is investigated and analyzed using damage data obtained from the 1995 Hyogoken-Nanbu earthquake. The analysis result and its comparison to the relationships for past earthquakes show that the average of the seismic performance has increased by 40-60% from 1948 to 1995, and that the collapse rate of 10% at the Hyogoken-Nanbu earthquake corresponds to that of 30% at the Fukui earthquake for the same overturning acceleration. Comparing the reported distribution of I=VII to the area with collapse more than 10%, historical continuity of the seismic intensity in JMA scale is discussed.

著者

入倉 孝次郎 釜江 克宏

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.52, no.1, pp.129-150, 1999-06-30 (Released:2010-03-11)

参考文献数

33

被引用文献数

9

---

We simulate strong ground motions during the 1948 Fukui earthquake with the JMA magnitude 7.1 based on a heterogeneous source model and the hybrid simulation technique. So far there are no existing source models available for simulating strong ground motions from the 1948 Fukui earthquake. Most of the source models have been assumed to have uniform slip distribution on rectangular fault plane. Such models could generate ground motions only available longer than several seconds, underestimating shorter period motions (<1sec) of engineering interest. The objective of this paper is to construct a heterogeneous source model for simulating strong ground motions in a broad period band during the 1948 Fukui earthquake. We assume two source models to examine: Model 1 is a reverse fault model determined from the analysis of geodetic data by YOSHIOKA (1974) and Model 2 is a normal fault model from strong motion displacement data by KIKUCHI et al. (1999). Heterogeneous slip distribution on fault plane is estimated based on the self-similar scaling relationships of seismic moment versus asperity areas and slips by Somerville et al. (1999). Then we obtained the standardized source model consisting of two asperities to have the average characteristics of asperities for the seismic moment of the Fukui earthquake. Relative locations and rupture times of the asperities on the fault plane are determined following the source model by KIKUCHI et al. (1999). The maximum asperity corresponding to the second event in their model has an area of 12×12km2 and slip of 1.7m and is located under the most heavily damaged area along the buried fault, known as the Fukui earthquake fault. The smaller asperity corresponding to the first event is located north of the maximum asperity. Rupture was initiated at the northern edge of the smaller asperity, propagated toward south, then broke to start the maximum asperity 7 seconds after the initial rupture. Large ground motions from both models, Model 1 and 2, are spread over the Fukui basin, although peak velocity distributions are rather different between the two models. Areas over 30% collapse ratio during the Fukui earthquake correspond to those with peak velocity over 60cm/s for Model 1 and over 80cm/s for Model 2. The level of the peak velocity in the areas with more than 30% collapse ratio are estimated to be over 80cm/s connected with both results by MOROI et al. (1998) and MIYAKOSHI and HAYASHI (1998). Pseudo velocity response spectra in the center of the Fukui basin for Model 2 have almost the same level of the observed ones at Takatori (TKT) and the simulated ones at Fukuike (FKI) within the damage belt during the 1995 Hyogo-ken Nanbu earthquake. We conclude that the damage distribution during the Fukui earthquake is well explained by strong ground motions simulated for Model 2 combined with the normal fault model by KIKUCHI et al.. (1999) and a standardized heterogeneous source model developed by SOMERVILLE et al. (1999).

著者

村松 郁栄

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.53, no.3, pp.269-272, 2001-03-25 (Released:2010-03-11)

参考文献数

13

著者

三好 崇之 石橋 克彦

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.60, no.2, pp.101-106, 2007-10-25 (Released:2013-08-20)

参考文献数

15

被引用文献数

2 2

著者

藤原 広行

出版者

SEISMOLOGICAL SOCIETY OF JAPAN

雑誌

地震 第1輯 (ISSN:00371114)

巻号頁・発行日

vol.66, no.4, pp.67-71, 2014

---

There is a similarity between the distribution of prime numbers and the pattern of earthquake occurrence. Earthquakes occur in a discrete manner in time and space. When viewed as a whole, however, we find some laws, such as Gutenberg-Richter law, that govern the entire earthquakes that seem to be individually independent. A similar phenomenon can be observed also in the world of number. The most basic example is the distribution of the prime numbers in integers. We consider a correspondence between earthquakes and prime numbers. We parameterize occurrence time of earthquakes as the prime numbers and magnitude of earthquakes as the interval of prime numbers. Then we obtain a relationship similar to Gutenberg-Richter law. We call the model obtained by this correspondence as "arithmetic seismic activity model". If we can parameterize earthquakes using prime numbers, knowledge that has been cultivated in the number theory can be used for understanding of earthquakes. The distribution of prime numbers is related to the distribution of zeros of Riemann zeta function. Researches are in progress to understand the zeros of the Riemann zeta function as an eigenvalue problem of quantum dynamical system. Earthquake may be modeled as a phenomenon corresponding to a change in the energy level of a quantum dynamical system associated with prime numbers.

著者

竹内 均 藤井 直之

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.25, no.2, pp.191-192, 1972-09-30 (Released:2010-03-09)

参考文献数

3

著者

松田 時彦 水本 匡起 田力 正好 松浦 律子

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.67, no.1, pp.35-39, 2014-06-16 (Released:2014-07-11)

参考文献数

14

被引用文献数

2 3

著者

武村 雅之 野澤 貴 池浦 友則

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.52, no.2, pp.317-333, 1999-10-20 (Released:2010-03-11)

参考文献数

30

被引用文献数

2

---

Nozawa et al. (1995) proposed a source model with two big subevents of the same seismic moment for the 1923 Kanto earthquake (M=7.9), through the simulation of the records by the Imamura-type strong motion seismograph (displacementmeter) at Gifu observatory. This model was named Model I in the present study. The first subevent of Model I is located under the Odawara city, having a fault plane with the strike of N290°E and the rake angle of 162°. This fault has much strike slip component, which is consistent with the focal mechanism solution by KANAMORI (1971). However, the direction of the strike is not compatible with the trench axis of the Sagami trough. The second subevent occurring 12s after the first subevent is located under the Miura Peninsula. The fault of the second subevent, having much dip slip component, well explains the geodetic data. Recently, the seismograms by the Imamura-type strong motion seismographs at Sendai (Mukaiyama) observatory and Yamagata observatory were examined and the instrumental responses of the seismographs were revealed. Crustal structure from source to stations was estimated in the present study so as to explain the observed Love and Rayleigh waves at Sendai (JMA) and Yamagata observatories from the recent events occurring near the focal region of the 1923 Kanto earthquake. However, Model I failed to explain the records of the 1923 Kanto earthquake at Sendai (Mukaiyama) and Yamagata observatories, using the obtained crustal structure. Then, we revised Model I to explain these records, in consideration of the newly determined focal mechanism solution by Lallemant et al.. (1996) and iso-depth contour of the upper boundary of the Philippine Sea plate by Ishida (1992). The first subevent of the revised model (Model R) has a fault plane with the strike of N321°E and the rake angle of 128°, and the twice of seismic moment of the second subevent. The direction of the fault strike of the first subevent is parallel to the trench axis of the Sagami trough, while the fault plane of the second subevent is the same as Model I. Model R succeeded in explaining not only the records at Sendai (Mukaiyama) and Yamagata observatories but also those at Gifu observatory in the period range from 2 to 20s. This shows the fault model, being in agreement with the geometry of subduction zone along the Sagami trough, is better to explain the seismic records observed in Japan.

著者

野澤 貴 武村 雅之 池浦 友則 山中 浩明

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.48, no.3, pp.331-340, 1995-11-25 (Released:2010-03-11)

参考文献数

30

被引用文献数

1

---

Records observed at Gifu observatory by an Imamura's type strong motion seismograph are one of the most useful records in Japan to investigate a source process of the 1923 Kanto earthquake (M=7.9). It is because amplitudes of the records are not saturated in EW and UD components, instrumental response of the seismograph has been clarified, and many records due to recent events occurred near the focal region of the Kanto earthquake have been obtained by more accurate seismographs at the same site. In the present study, a source process of the 1923 Kanto earthquake is elucidated through a simulation of the records using the normal mode theory in the period range from 2 to 20s. First, a crustal structure from the source to the station is estimated so as to explain dispersive characteristics of Love waves observed at Gifu observatory for the recent events, and their records are simulated to confirm a validity of the estimated crustal structure. Secondly, the records from the Kanto earthquake are simulated using the obtained crustal structure to deduce the source process of this event. According to KANAMORI (1971), a macroscopic faulting is a reverse right-lateral fault on a plane dipping 34° towards N20°E, whose slip has much strike component. If two big subevents with the same focal mechanism obtained by KANAMORI (1971) and with a time interval of about 12s are assumed on the fault plane, the observed records can be well explained. The first subevent is located under the Odawara city and the second one under the Miura Peninsula. The focal depth of the second event is 15 to 35km being deeper than that of the first event, which is 5 to 25km in depth. The seismic moments and the rise time are assumed 2.5×1027 dyne-cm and 5s for both the events respectively. On the other hand, if the focal mechanism of the second event is dip slip type, the observed records can be also explained well, even though the focal depth of the second subevent is the same as that of the first one. This model is consistent with a slip distribution on the fault plane obtained from geodetic data.

著者

武村 雅之 諸井 孝文

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.53, no.3, pp.285-302, 2001-03-25 (Released:2010-03-11)

参考文献数

28

被引用文献数

4

著者

武村 雅之 野澤 貴

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.49, no.3, pp.375-387, 1996-11-23 (Released:2010-03-11)

参考文献数

13

被引用文献数

3

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Seismograms from the 1923 Kanto earthquake (M=7.9) and its aftershocks at the Yamagata observatory of JMA (The Japan Meteorological Agency) in Tohoku district, Japan, are examined. They were recorded by the Imamura-type strong motion seismograph. Horizontal-component records from the main shock and the 1924 Tanzawa earthquake (M=7.3), one of the largest aftershocks, are digitized and the instrumental characteristics of the seismographs are examined. Natural period To and damping ratio v of the instrument are evaluated to be 4.5s and 1.5 for both the NS and EW components from the free oscillation records and documents for the results of testing the instrumental response. The maximum displacement in EW component of 11.2cm is obtained for the main shock in the period range from 2 to 20s, after the instrument correction.On the other hand, uncertainties of the instrumental characteristics remain for the seismograms from the 1923 Kanto earthquake observed at the Mukaiyama observatory of the Tohoku Imperial University in Sendai, [TAKEMURA et al. (1995)]. The Sendai city is located about 40km east from the Yamagata city. The epicentral distance and azimuth of the Mukaiyama observatory is not so different from those of the Yamagata observatory for the 1923 Kanto earthquake. It is found that the displacement records at Sendai and Yamagata have mostly the same amplitude for the recent moderately large earthquakes with almost the same location of epicenter as the 1923 Kanto earthquake. All the records were observed by the strong motion displacement seismographs of To=6s and v=8 both at the Yamagata observatory and at the Sendai district meteorological observatory of JMA. This fact indicates that the displacement at the Mukaiyama observatory in Sendai ought to show almost the same amplitude as one at the Yamagata observatory during the 1923 Kanto earthquake. Then, we redetermined To of the instrument at Mukaiyama observatory so that the amplitude of the displacement after the instrument correction is the same as that at the Yamagata observatory. Redetermined To is 5s in EW component, being meaningfully longer than the results estimated by TAKEMURA et al. (1995).

著者

野澤 貴 武村 雅之

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.50, no.1, pp.11-20, 1997-05-28 (Released:2010-03-11)

参考文献数

12

被引用文献数

1

---

Records observed at the Takada observatory by an Imamura's type strong motion seismograph are useful in Japan to investigate a source process of the 1923 Kanto earthquake (M=7.9). Ground motion in the vertical component is completely recorded to the end. Those in horizontal components are also recorded to the end, though the amplitudes of them are saturated in the midst of the records. The instrumental response of the seismograph has been already clarified by TAKEMURA and NOZAWA (1996), and many records from the recent earthquakes occurring near the focal region of the Kanto earthquake are also obtained at the same site with modern instruments. First, a crustal structure model from the source to the station is established so as to explain the dispersion characteristics of Love-waves observed for the recent earthquakes, and their records are simulated by the normal mode theory using the obtained structure to confirm its validity. Secondly, the records from the Kanto earthquake are reproduced using the same structure model. NOZAWA et al. (1995) proposed the two possible source models for the Kanto earthquake through the simulation of the records at the Gifu observatory. Two big subevents with a time interval of about 12s are assumed on the fault plane in both the models, while the focal mechanism and the focal depth of the second subevent are different between these models. It is found that these models similarly explain the records at the Takada observatory from the Kanto earthquake. The maximum displacements of the reproduced horizontal ground motions are estimated about 20cm in NS component. and about 10cm in EW component. These results are consistent with the fact that the amplitudes of the records in NS component are strongly saturated compared with those in EW component.