著者

Takane Hori

出版者

The Seismological Society of Japan, The Volcanological Society of Japan, The Geodetic Society of Japan

雑誌

Journal of Physics of the Earth (ISSN:00223743)

巻号頁・発行日

vol.44, no.4, pp.349-356, 1996 (Released:2009-04-30)

参考文献数

18

被引用文献数

12 20

---

To evaluate the temporal variation of seismicity in the Inner Zone of Southwest Japan before and after the Nankai trough events, we introduced a statistical model and estimated the value of the model parameters. We used the data of disastrous earthquakes to estimate them. Because of the lack of spatially sufficient data, we used data from the 9th century in the case of the northern Kinki region, and in the case of the whole Inner Zone of Southwest Japan only data after the 17th century. The results show that for the northern Kinki region the seismicity has a peak before the Nankai trough events, although there is no significant change before them in the whole Inner Zone of Southwest Japan. The seismicity in the Inner Zone of Southwest Japan increases just after the Nankai trough events. We compared the obtained intensity functions with the recent JMA data from 1885 to 1995. The seismicity seems to have increased in the last 30 years. Using data from this period, we estimated the occurrence time of the next Nankai trough event. Our results show that it will occur in the 2030'S.

著者

Zhengmeng LI

出版者

The Seismological Society of Japan, The Volcanological Society of Japan, The Geodetic Society of Japan

雑誌

Journal of Physics of the Earth (ISSN:00223743)

巻号頁・発行日

vol.34, no.Supplement, pp.S91-S102, 1986 (Released:2009-04-30)

参考文献数

17

---

Just before the large earthquakes in Bohai, Haicheng, Luhuo, Tangshan, and Songpan in northern and southwestern China, anomalous changes in radon content in groundwater from wells and springs were recorded at most of the observation stations. From the compilation of the records of radon anomalies, characteristic features of the imminent radon changes prior to a large earthquake are derived: (1) spike-like anomalous changes; (2) inhomogeneity of the spatial distribution of the anomalies around the epicentral area; and (3) migration and spatiotemporal evolution of anomalies. Understanding of the characteristics of radon anomaly is of importance and will contribute much to the prediction of an impending large earthquake.

著者

Tokuji Utsu Yosihiko Ogata Ritsuko S Matsu'ura

出版者

The Seismological Society of Japan, The Volcanological Society of Japan, The Geodetic Society of Japan

雑誌

Journal of Physics of the Earth (ISSN:00223743)

巻号頁・発行日

vol.43, no.1, pp.1-33, 1995 (Released:2009-04-30)

参考文献数

139

被引用文献数

587 968

---

The Omori formula n(t)=K(t+c)-1 and its modified form n(t)=K(t+c)-P have been successfully applied to many aftershock sequences since the former was proposed just 100 years ago. This paper summarizes studies using these formulae. The problems of fitting these formulae and related point process models to observational data are discussed mainly. Studies published during the last 1/3 century confirmed that the modified Omori formula generally provides an appropriate representation of the temporal variation of aftershock activity. Although no systematic dependence of the index p has been found on the magnitude of the main shock and on the lowest limit of magnitude above which aftershocks are counted, this index (usually p = 0.9-1.5) differs from sequence to. sequence. This variability may be related to the tectonic condition of the region such as structural heterogeneity, stress, and temperature, but it is not clear which factor is most significant in controlling the p value. The constant c is a controversial quantity. It is strongly influenced by incomplete detection of small aftershocks in the early stage of sequence. Careful analyses indicate that c is positive at least for some sequences. Point process models for the temporal pattern of shallow seismicity must include the existence of aftershocks, most suitably expressed by the modified Omori law. Among such models, the ETAS model seems to best represent the main features of seismicity with only five parameters. An anomalous decrease in aftershock activity below the level predicted by the modified Omori formula sometimes precedes a large aftershock. An anomalous decrease in seismic activity of a region below the level predicted by the ETAS model is sometimes followed by a large earthquake in the same or in a neighboring region.

著者

Jim MORI Thomas BOYD

出版者

The Seismological Society of Japan, The Volcanological Society of Japan, The Geodetic Society of Japan

雑誌

Journal of Physics of the Earth (ISSN:00223743)

巻号頁・発行日

vol.33, no.3, pp.227-240, 1985 (Released:2009-04-30)

参考文献数

22

被引用文献数

4 7

---

The Niigata earthquake of June 16, 1964. (M8=7.5) is studied using a body-wave inversion technique on teleseismic P waveforms of the mainshock and a joint hypocenter determination of 27 of the largest (MJMA≥4.0) regionally recorded aftershocks. The mainshock is interpreted as being composed of two subevents with moments of 2.1×1026 dyn-cm and 2.0×1027 dyn-cm. The focal mechanism indicates that faulting could have occurred on either a plane dipping toward the west or a plane dipping toward the east. The initial subevent is located at a depth of 8 to 13 km, while the centroid of the second sub-event is located 27 km southwest of the first and at a depth of 3 km. The relocated aftershocks all appear to have depths of less than 15 km which is consistent with the depths obtained for the mainshock. They appear to define a trend dipping shallowly toward the east which is consistent with the relative locations of the two subevents comprising the mainshock. We conclude, therefore, that a fault plane dipping toward the east is more consistent with the relative locations of the two subevents and the relocations of the aftershocks.

著者

Yasumaro Kakehi Tomotaka Iwata

出版者

The Seismological Society of Japan, The Volcanological Society of Japan, The Geodetic Society of Japan

雑誌

Journal of Physics of the Earth (ISSN:00223743)

巻号頁・発行日

vol.40, no.6, pp.635-655, 1992 (Released:2009-04-30)

参考文献数

32

被引用文献数

8 7

---

The fault plane model was constructed and the rupture process of the 1945 Mikawa earthquake (M=6.8) was determined from strong motion records. To date, two fault plane models have been reported, one of which uses geodetic data and the other the aftershock distribution. The fault plane model presented here is a thrust that strikes NNW-SSE with a small right-lateral component. It explains the strong motion records, surface fault traces, aftershock distribution, and geodetic data. Rupture started at the deepest and southernmost point on the fault plane and propagated radially. The values of the slip and seismic moment were 3.0 m and 1.0 × 1026 dyne cm. The possibility is shown that the Mikawa earthquake was a multiple shock. The faulting motion of the Mikawa earthquake determined here, which is estimated to have been caused by a WWS-EEN compressional stress, cannot be explained by the stress field caused by the subduction of the Philippine Sea Plate alone. Another factor that produced a WWS-EEN compressional stress field in this area is believed to have had an important role during the stress accumulation process of the Mikawa earthquake.

著者

Yoko OTA Torao YOSHIKAWA

出版者

The Seismological Society of Japan, The Volcanological Society of Japan, The Geodetic Society of Japan

雑誌

Journal of Physics of the Earth (ISSN:00223743)

巻号頁・発行日

vol.26, no.Supplement, pp.S379-S389, 1978 (Released:2009-04-30)

参考文献数

39

被引用文献数

9 19

---

In the Japanese coastal area, deformation patterns deduced from the height of former shorelines are classified into four types, A, B, C and D, each reflecting different response of tectonic regions to island arc movements. Each area has been progressively and acceleratedly deformed in a same pattern during the late Quaternary. Maximum rate of average uplift is 1.5m/1, 000 years for the Last Interglacial terrace and 4m/1, 000 years for the Holocene terrace.The landward tilting, type D, on the Pacific coast of Southwest Japan has been associated with great earthquakes occurring below the inner slope of the Nankai Trough. Type D area is separated from upwarping mountains by hinge lines along which subsidence has accumulated. Tectonic basins filled with younger sediments on the continental slopes are assumed to be depressed zones along the former hinge lines. Ages of deformed shorelines suggest that until the early Pleistocene seismic deformation had affected only the continental slopes and later propagated onto the coastal area in the late Pleistocene at the latest, resulting in the intensification of deformation of former shorelines. In contrast, type C deformation has predominated on the Pacific coast of Northeast Japan, which are 200km distant from the Japan Trench and seem to be still located landward of hinge lines of seismic crustal movement.

著者

Yoshimitsu Fukushima Kojiro Irikura

出版者

The Seismological Society of Japan, The Volcanological Society of Japan, The Geodetic Society of Japan

雑誌

Journal of Physics of the Earth (ISSN:00223743)

巻号頁・発行日

vol.45, no.2, pp.135-146, 1997 (Released:2009-04-30)

参考文献数

20

被引用文献数

5 6

---

The peak horizontal acceleration and velocity of observed records from the 1995 Hyogo-ken Nanbu earthquake are compared with those predicted from empirical attenuation relations that were derived to be applicable to near-source areas. We found that the observed peak values matched well the empirical attenuation relations. The observed peak vertical accelerations were about half the peak horizontal accelerations when less than 100 cm/s/s. But, the observed peak vertical accelerations tended to be more than half the horizontal ones beyond 100 cm/s/s, and at some sites on soft soil, the peak vertical accelerations were greater than the peak horizontal accelerations. On the other hand, most of the observed peak vertical velocities were about 40% of the peak horizontal velocities independent of the peak amplitudes. At Port Island in Kobe City, remarkable non-linear behavior of soft soil was observed in the vertical array records. The high-frequency shear waves decreased due to liquefaction and the peak horizontal accelerations decayed at the surface. On the contrary, vertical ground motion was amplified by the strong contrast of P-wave velocity in the surface soils. This fact may be one of the causes for greater peak vertical acceleration than peak horizontal acceleration.

著者

Naoshi Hirata Shiro Ohmi Shin'ichi Sakai Kei Katsumata Satoshi Matsumoto Tetsuo Takanami Akira Yamamoto Takashi Iidaka Taku Urabe Mayumi Sekine Tooru Ooida Fumihito Yamazaki Hiroshi Katao Yasuhiro Umeda Masao Nakamura Norihiko Seto Takeshi Matsushima Hiroshi Shimizu Japanese University Group of the Urgent Joint

出版者

The Seismological Society of Japan, The Volcanological Society of Japan, The Geodetic Society of Japan

雑誌

Journal of Physics of the Earth (ISSN:00223743)

巻号頁・発行日

vol.44, no.4, pp.317-328, 1996 (Released:2009-04-30)

参考文献数

21

被引用文献数

41 43

---

A disastrous earthquake with a magnitude of 7.2 hit the southern part of Hyogo Prefecture on January 17, 1995. The mainshock was located on an active fault of the Arima-Takatsuki-Rokko fault system. Its focal mechanism was consistent with a right-lateral strike-slip fault trending N40°E. Three days after the occurrence of the mainshock, we started to install a highly dense seismic array in and around the fault area of the quake. Two permanent regional seismic networks of more than 30 stations covered the entire area of 200 km × 200 km. The temporarily installed array of 27 stations spanned the fault area of 15 km × 50 km. All data were telemetered to a temporary observation center at Uji. We located about 3, 100 aftershocks in real time for 1 month using an Internet connection between seismic networks. The aftershock area extended 70 km trending northeast to southwest. Hypocenters determined by the network were delivered automatically through the Internet. We found that the aftershock distribution was heterogeneous in space and time: seven clusters of hypocenters were identified and temporary variation in the rate of occurrence of aftershocks had a periodic component with periods of a half of day, 1 day, and 3 days, that are superimposed on decaying of the rate following Omori's law.

著者

Keiiti AKI

出版者

The Seismological Society of Japan, The Volcanological Society of Japan, The Geodetic Society of Japan

雑誌

Journal of Physics of the Earth (ISSN:00223743)

巻号頁・発行日

vol.4, no.2, pp.53-62, 1956 (Released:2009-04-30)

参考文献数

6

被引用文献数

2 5

---

In connection with the earthquake energy problem, the thermal processes which can result in the steady accumulation of necessary energy somewhere close to the bottom of the earth's crust has been investigated. With the aid of experimental and theoretical laws concerning thermal convections, some informations about the physical state at the place have been obtained.

著者

Robert C. BOSTROM

出版者

The Seismological Society of Japan, The Volcanological Society of Japan, The Geodetic Society of Japan

雑誌

Journal of Physics of the Earth (ISSN:00223743)

巻号頁・発行日

vol.29, no.2, pp.145-161, 1981 (Released:2009-04-30)

参考文献数

29

被引用文献数

1 2

---

Flexure of the mantle by the east-west M2 wave imposes non-reversing small body torques. The stress and displacement have been evaluated for the plausible range of the elastic quality factor Q. The non-cancelling stresses are of the order 5×10-7dyn/cm2, varying as the magnitude of Q-1. The displacement varies as Q-2 and is correspondingly minute, but is cumulative through geologic time. The role of the lithosphere becomes dominant, because stress diffusion causes it to act as a transmission channel. Stress acting on isostatic lithosphere is additive horizontally, as wind stress is additive across a floating ice sheet. In respect to oceanic lithosphere, within a period of about 106 years the stress reaches a value of tens of bars and its displacement rate several cm/yr. It is surmised that the values reached are limited by imperfect elasticity of the lithosphere. The energy consumption based upon gravimetric values of the phase lag, between 1.3 and 2.3×1026erg/yr, is a fraction of the dissipation astronomically observed but not found in the seas. The effect of lithosphere creep is compared with Pacific and Atlantic tectonic features.

著者

Chuji TSUBOI

出版者

The Seismological Society of Japan, The Volcanological Society of Japan, The Geodetic Society of Japan

雑誌

Journal of Physics of the Earth (ISSN:00223743)

巻号頁・発行日

vol.4, no.2, pp.63-66, 1956 (Released:2009-04-30)

参考文献数

7

被引用文献数

91 103

---

Various facts appear to suggest that one continuous field of mechanical stress developed in the earth's crust has a certain upper limit for its voluminal extent. The ultimate mechanical stress energy that can be stored up in this whole volume until a break-down takes place in it may be identified with the energy of the largest possible earthquake. The energy deduced on this hypothesis agrees well with those of the actual largest earthquakes. The area A in which aftershocks occur in association with a major earthquake has been found by UTSU and SEKI regularly to increase with the magnitude M of that main shock. This relation, when combined with the magnitude-energy relation due to GUTENBERG and RICHTER, yields a formulaE=6×102×A1·5.The numerical values of the coefficient and of the exponent of A in this formula can be well explained by the hypothesis stated above regarding the spatial distribution of the stress energy within the earth's crust.

著者

Ichiro OHNO

出版者

The Seismological Society of Japan, The Volcanological Society of Japan, The Geodetic Society of Japan

雑誌

Journal of Physics of the Earth (ISSN:00223743)

巻号頁・発行日

vol.24, no.4, pp.355-379, 1976 (Released:2009-04-30)

参考文献数

8

被引用文献数

287 380

---

A theory was developed on the free vibration of a crystal of rectangular parallelepiped and of general symmetry by extending Demarest's theory of cube resonance. All vibrational modes were classified and described in detail for the case of orthorhombic symmetry. The theory is applied to determine elastic constants of crystals from the resonance frequencies of its free vibrations. The method of numerical analysis of resonance frequency data was studied to derive a practical way of elastic constant determination. As an example, the elastic constants of two specimens of single crystal olivine (Mg1.8Fe0.2SiO4) were determined. The applicability of the resonance method is largely extended by the present theory to the precise determination of elastic constants of single crystals.

著者

Ichiro Kawasaki Yasuhiro Asai Yoshiaki Tamura Takeshi Sagiya Naoya Mikami Yoshimitsu Okada Masaharu Sakata Minoru Kasahara

出版者

The Seismological Society of Japan, The Volcanological Society of Japan, The Geodetic Society of Japan

雑誌

Journal of Physics of the Earth (ISSN:00223743)

巻号頁・発行日

vol.43, no.2, pp.105-116, 1995 (Released:2009-04-30)

参考文献数

22

被引用文献数

78 98

---

We report the detection of a large ultra-slow earthquake. Subsequent to the July 18, 1992, Sanriku-Oki, Japan, earthquake (Ms6.9, 39.42°N, 143.33°E), a clear post-seismic phase appeared in the crustal strains recorded by quartz-tube extensometers at Esashi (Δ=174 km, φ = -99°, from the NEIC CMT source). We have decomposed the crustal strains into atmospheric pressure effects, tides and trends by the Bayesian tidal analysis method. The EW component of the trend thus extracted displays a clear quasi-static increase of -4 x 10-8 with a time constant of about one day. This is about four times greater than the co-seismic strain step. We have investigated the cause of the post-seismic phase to conclude that this was not due to local disturbances. A similar post-seismic phase of -15 x 10-8 was also observed in the EW component of crustal strain records at Miyako (Δ =117 km, φ = - 80° ), Tohoku University. From the close similarity between the post-seismic waveforms at Esashi and Miyako, we attribute the post-seismic phase to the ultra-slow faulting subsequent to the seismic event. We have inverted the strain steps to obtain a solution of an interplate low-angle thrusting located about 54 km to the east from the NEIC CMT epicenter with a moment release of up to (1-4) x 1020 m, which corresponds to that of a MW7.3-7.7 seismic event.

著者

Toshihiko HASHIDA Kunihiko SHIMAZAKI

出版者

The Seismological Society of Japan, The Volcanological Society of Japan, The Geodetic Society of Japan

雑誌

Journal of Physics of the Earth (ISSN:00223743)

巻号頁・発行日

vol.35, no.5, pp.367-379, 1987 (Released:2009-04-30)

参考文献数

16

被引用文献数

2 3

---

Predictions of seismic intensities are attempted based on a three-dimensional attenuation structure and amplifying factors at stations obtained in the previous study for the Tohoku district, Japan. An empirical relation between `earthquake size' related to the intensity and JMA magnitude MJ is also used. The first prediction is to map spatial distribution of the minimum magnitude MJ of an earthquake which causes intensity 5 at a specific JMA station. The result shows that the effects of regional variation of attenuation and local site condition at the station are important in assessing the seismic hazard. Another attempt is made to predict an annual number of felt earthquakes at each JMA station based on the JMA earthquake catalogue for a period from 1963 to 1984. A comparison of predicted number with the observed one shows a good coincidence between them for each year. This may suggest that the proposed method can successfully predict intensities. However, a comparison of the predicted cumulative number for each intensity grade with the observed one shows that the cumulative numbers for intensities 2, 3, and 4 are underestimated by the proposed method. This result may suggest a nonlinearity between the JMA intensity scale and the logarithm of acceleration, which has been suggested by other evidences.

著者

Hiroshi Katao Naoki Maeda Yoshihiro Hiramatsu Yoshihisa Iio Setsuro Nakao

出版者

The Seismological Society of Japan, The Volcanological Society of Japan, The Geodetic Society of Japan

雑誌

Journal of Physics of the Earth (ISSN:00223743)

巻号頁・発行日

vol.45, no.2, pp.105-119, 1997 (Released:2009-04-30)

参考文献数

11

被引用文献数

42 49

---

Earthquake focal mechanisms before and after the 1995 Hyogo-ken Nanbu earthquake have been investigated using seismic records from regional seismic networks. Before the mainshock, seismicity was very active at the Tamba Plateau, a neighboring area of the Hyogo-ken Nanbu earthquake rupture zone. In contrast, the seismicity along the Hyogo-ken Nanbu earthquake rupture zone was not so active. Most earthquakes in these regions had source mechanisms of E-W compression and were of the strike-slip or reverse-fault type. Most aftershocks along the Hyogo-ken Nanbu earthquake rupture zone have strike-slip solutions with P-axis in the E-W or ESE-WNW direction, which is compatible with the trend of aftershock distribution and the strike of active faults the same as the mainshock mechanism. Simultaneously, many other aftershocks were of the reverse-fault type with E-W compression. This area is still controlled by the regional stress field of E-W compression observed before the mainshock. Although, we could find various types of mechanisms in the aftershock sequence, some normal fault-type events were also observed in the mainshock rupture zone. We could find events of SE-NW compression, and this direction is nearly perpendicular to the trend of the mainshock rupture zone. Some aftershocks that occurred near the epicenter of the mainshock had solutions of N-S compression. The geometry of the active fault systems and/or local stress change induced by the mainshock may cause these complex features of focal mechanisms. After the mainshock, the focal mechanisms of earthquakes in the Tamba Plateau were approximately E-W compressional; the same as that before the mainshock.