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This paper introduces the concept of co‐renovation, which involves creating a network of people, objects, and events during the renovation process. The study examines the effectiveness of co‐renovation in two ways. First, by promoting an open approach to the renovation process and the resulting house, it is possible to stimulate connections between those involved in the renovation. Second, the creation of a renovation network can encourage a sense of community development, leading to independent regional initiatives that extend beyond the renovation project. To optimize the effectiveness of co‐renovation, it is crucial to foster spontaneous connections, and this paper provides a summary of the factors that contribute to this. [ABSTRACT FROM AUTHOR]

This paper focuses on the ultimate state of three‐story wood dwellings with high aspect ratios, which are increasing in Japan's urban areas. Using shaking table test results from the 2019 full‐scale shaking table test, a comprehensive study is conducted on the accuracy of evaluating ultimate state through the story shear failure mode at the first story, the tension fracture mode at the wall base of the first story, and foundation sliding mode on the soil. Methods evaluating the dynamic response behaviors of the building systems are also investigated. In the test, the current Japanese seismic design guidelines were applied, and two Grade‐3 buildings were prepared. One adopted the Post‐and‐Beam structure (A‐building), and the other the Shear‐Wall structure (B‐building). A series of tests planned very different physical boundary conditions surrounding their reinforced concrete (RC) mat foundations. The sills, column bases and wall bases of the upper wood structures were anchored to the RC foundations by steel anchor bolts, according to the current Allowable Stress Design (ASD) requirements. In the first stage, A‐building equipped a Base‐Isolation system, while B‐building represented a generic foundation constructed on a 1.5 m‐height real soil ground by preparing a rigid soil box (Foundation‐Soil system). In the second stage of A‐building and B‐building, the foundation was firmly fixed (Fixed‐Foundation system), and shaking table motions were fully applied to the foundations. The entire test system was setup on the large shaking table facility at E‐Defense, and a series of tests were conducted using JMA‐Kobe motion and JR‐Takatori motion recorded in the 1995 Kobe earthquake as Maximum‐Considered‐Earthquake motions. Confirmed was the change in the structural mechanism due to the upper structural systems and the foundation boundaries. Regarding the upper wood structure performance in the Fixed‐Foundation system, a story shear failure mode was observed at the first story in A‐building, while a tension fracture mode at the base of the first story in B‐building. This difference of failure mode is difficult to determine with ASD. The maximum strength were more than four times higher than the ASD base shear force. Tension fracture capacity at the wall base was mainly enhanced by the presence of the steel anchor bolts. Regarding the foundation performance in Foundation‐Soil system of B‐building, a horizontal displacement up to 240 mm was observed between the foundation and soil when JMA‐Kobe 100% was applied. A response reduction effect was observed in the upper wood structure, similar to the Base‐Isolation system of A‐building. The initial friction and cyclic friction strength capacities between the foundation and soil were quantitatively evaluated considering the horizontal two‐directional sliding. The representative test results were converted to the corresponding SDOF systems based on the first mode response assessment. In the Fixed‐Foundation system, the dynamic response characteristics of the upper wood structures were properly represented using Ibarra‐Medina‐Krawinkler pinching model in the equivalent SDOF system. [ABSTRACT FROM AUTHOR]

Summary: The mega‐subcontrolled structural system (MSCSS) was proposed in the past decade as a new construction technique for high‐rise buildings because it showed an improved structural seismic response. However, research continues to focus on further increasing the response control ability, minimizing the cost, and improving the seismic performance of MSCSS. In this paper, a novel configuration named configuration 13 is proposed that incorporates an inverted V‐bracing (chevron) along the height in the center of the structure, and a mid‐story isolation system is situated under the first mega‐beam. The response control analysis and dynamic characteristics of the novel MSCSS are studied based on the structural responses to seven seismic waves. This novel configuration shows a significant improvement of at least 30.58% in the structural acceleration response with an average overall improvement of 49.7% under an El Centro wave. Moreover, nonlinear dynamic analysis is performed under the same seven waves; the proposed configuration shows the maximum pseudo‐spectral acceleration under the El Centro input at low frequencies, while under the Kobe wave, acceleration peaks also appear at higher frequencies. Furthermore, the Hilbert–Huang transform is also applied, confirming that the proposed MSCSS shows no sudden fluctuations in its structural response under seismic excitation. [ABSTRACT FROM AUTHOR]

This study identifies some of the distinctive characteristics of the land acquired by foreigners in the zakkyochi (mixed‐residential areas) of Kobe, Japan, during the Meiji era, and explores the various means by which foreigners were able to acquire this land. The primary focus is on Kitano‐cho and Yamamoto‐dori, a well‐known residential area for foreigners, where ijinkan (historical Western‐style residences) still stand to this day. By law, foreigners in zakkyochi were given only the right to lease land from Japanese citizens and the Japanese government. Nonetheless, foreigners such as E.H. Hunter expanded the area available to them by using the names of Japanese relatives. Although Japanese women who married foreigners were also prohibited from owning land, this restriction did not apply to their children. Thus, in the case of E.H. Hunter, a significant portion of the land he acquired was acquired in the name of his children, primarily in areas adjacent to the mountains, excluding the sites of graveyards and villages. Indeed, it was generally the case that the land used by foreigners in Kobe was concentrated in the hilly areas with good views that did not serve as graveyards or village sites. [ABSTRACT FROM AUTHOR]

After the earthquakes of Kobe (1995) and Northridge (1994) many research efforts have focused the attention on the seismic behaviour of partial strength beam‐to‐column joints because, in these seismic events, brittle fractures of welds of full‐strength joints belonging to MRFs have been observed. One of the most popular solutions developed in the aftermath to overcome the drawbacks of the typical welding joint details consisted in the adoption of the so‐called Reduced Beam Section (RBS) strategy. With this strategy beam ends are weakened into areas located sufficiently far from the column in order to reduce the stress concentration in the welds. Nevertheless, while many experimental efforts have been devoted to this connection typology, the available experimental results on full‐scale structures are still quite limited. Within this framework, aiming to provide a contribution to fill this knowledge gap, an experimental program concerning the pseudo‐dynamic testing of a full‐scale two‐storey steel building equipped with five different connection typologies is currently undergoing at the University of Salerno. In this paper the results of the first experimental campaign, dealing with MRFs with RBS connections, are presented. The mock‐up has been subjected to a sequence of seven accelerograms and the results have confirmed that, if properly designed, RBS connections provide large energy dissipation capacity and plastic rotation supply. Nevertheless, the failure of welds due to damage accumulation can be still possible, even adopting full penetration butt joint welding details conforming to Eurocode 3 and Eurocode 8 provisions. The experimental results have been complemented with numerical analyses developed with the software SeismoStruct. The comparisons between the numerical simulations and the experimental results show that the applied mixed distributed and concentrated plasticity approach, based on the adoption of phenomenological spring models, can capture accurately the global response of the structure, but it predicts with lower accuracy the local response parameters. [ABSTRACT FROM AUTHOR]

The devastating earthquake that struck the City of Kobe on 17 January, 1995, created many critical issues for the government of Japan. The Kobe shock pointedly revealed that both the central and local governments had neglected to develop the administrative skills necessary for managing major disasters. This paper, first, provides brief background information on the Kobe disaster. It is followed by a discussion of the problems of the Self-Defense Forces and its involvement in Japan’s crisis management. The paper then describes the function of executives at a time of crisis. In the final section, the paper outlines subsequent government efforts to improve the quality of crisis control in Japan. [ABSTRACT FROM AUTHOR]

Aim: Owing to the stress caused by the behavioral restrictions and lifestyle changes during the COVID‐19 pandemic, suicide rates have increased in Japan, especially among young people. This study aimed to identify the differences in the characteristics of patients hospitalized for suicide attempts in the emergency room, requiring inpatient care before and during the pandemic over 2 years. Methods: This study was a retrospective analysis. Data were collected from the electronic medical records. A descriptive survey was conducted to examine changes in the pattern of suicide attempts during the COVID‐19 outbreak. Two‐sample independent t‐tests, Chi‐square tests, and Fisher's exact test were used for data analysis. Results: Two hundred one patients were included. No significant differences were found in the number of patients hospitalized for suicide attempts, average age, or sex ratio before and during the pandemic periods. Acute drug intoxication and overmedication in patients increased significantly during the pandemic. The self‐inflicted means of injury with high fatality rates were similar during the two periods. The rate of physical complications significantly increased during the pandemic, while the proportion of unemployed individuals significantly decreased. Conclusions: Despite studies predicting an increase in suicides based on past statistics of young people and of women, no significant changes were observed in this survey of the Hanshin‐Awaji region, including Kobe. This may have been owing to the effect of suicide prevention measures and mental health measures implemented by the Japanese government after an increase in suicides and after past natural disasters. [ABSTRACT FROM AUTHOR]

The Clydach Valley Subgroup (Courceyan) records a dip section through an Early Carboniferous shallow marine, carbonate shelf and consists of three oolitic formations separated by paludal/peritidal units with abundant evidence of subaerial exposure in proximal areas. The lower part correlates with the Kinderhookian–Osagean Boundary Excursion, with allochem data indicating a minimum δ13C value for marine carbonate of +4.5‰, with associated δ18O of −4.6‰. Marine carbonate δ13C and δ18O values of +2‰ and −2‰, respectively, were estimated for the younger part. Allochem isotopic data yield a well‐defined mixing line consistent with stabilisation in meteoric water at varied water: rock ratios, the degree of stabilisation increasing up‐dip and up‐stratigraphy. Two distinct diagenetic styles closely correlate with evidence for the presence (Diagenetic Regime 1) or absence (Diagenetic Regime 2) of subaerial exposure, non‐ferroan and ferroan calcite cement dominating respectively. Five cement zones (Zones 2–6) defined by iron content occur in Diagenetic Regime 1, irrespective of formation, indicating a similar sequence of palaeohydrological changes affected repeated depositional cycles. Zones 3–5 are considered meteoric based on their isotopic composition (δ18O: −5.8 to −11.1‰ and δ13C: −3.7 to −6.2‰) and form distinct clusters dependent on zone, age and location. Pedogenic carbonates and meteoric cements record a long term increase in meteoric δ18O values: −7.8‰ during the Kinderhookian–Osagean Boundary Excursion, −6.9‰ during diagenesis of the upper part of the subgroup and −6.3‰ associated with initial deposition of the overlying Llanelly Formation. This is consistent with global sea water trends, but an element of climate change cannot be ruled out. Increases in cement δ18O values as meteoric systems become established (Zone 3–4) indicate repeated short term variation in rainwater composition probably driven by climate change, but also suggests a link between climate and the depositional cycle. [ABSTRACT FROM AUTHOR]

Summary: The present study aims to identify damage in two‐dimensional (2‐D) moment frames using seismic responses by combining the random forest (RF) machine classifier and the enhanced gray wolf optimizer (EGWO) metaheuristic algorithm. First, a 2‐D moment frame for the dynamic analysis is simulated using the finite element method (FEM). Then, the placement of sensors is optimized using a proposed optimal sensor placement (POSP) method, which is a combination of the iterated improved reduced system (IIRS) and the binary differential evolution (BDE) optimization algorithm. The acceleration responses of the moment frame having damaged elements under 1995 Kobe earthquake are measured at the optimal sensor placement. Then, the natural frequencies and mode shapes of the structure are extracted using the auto‐regressive model with exogenous input method (ARX) as a system identification method. The natural frequencies are exploited to train an RF machine learning network that can find the damaged story of the moment frame. Then, EGWO is employed to accurately locate and quantify the damaged elements of the structure. The efficiency of the proposed method is assessed through considering a six‐story frame with 18 elements, a seven‐story frame with 49 elements, and the experimental data of an eight‐story frame for various conditions. The results show that the RF algorithm has an outstanding performance to correctly find a damaged story. Furthermore, the location and severity of damaged elements are precisely determined by EGWO algorithm. As a final outcome, it is demonstrated that the two‐step proposed method is very effective in seismically identifying damage to such structures. [ABSTRACT FROM AUTHOR]

A method for formulating a rational reorganizing plan was examined. The first approach involved statistically determining the reorganization priority, which was applied to all public housing residential buildings in Kobe city to confirm its effectiveness. The second approach entailed creating a program that automatically ranks all combinations of housing units under consideration for reorganization, based on the required reconstruction costs and the potential for reducing the number of dwelling units and buildings. When this program was applied in the area, it yielded combinations of housing units that could reorganize more dwelling units at a lower cost. [ABSTRACT FROM AUTHOR]

The COVID‐19 pandemic is an outstanding global threat for both human health and well‐being. Under the pandemic, green spaces are known to mitigate the physical/mental stress of urban people. However, it remains unclarified how blue spaces such as coastal and river areas play a role in healing urban people's health and well‐being during the pandemic.Here, conducting an online‐based survey in Japanese megacities, with 5756 responses received from residents of Tokyo, Yokohama, Osaka and Kobe, we examined the effects of personal characteristics of city residents on their visitation frequencies to blue spaces during and after the emergency periods, and compared visitation purposes and motivation between the coastal and river areas. Cumulative linear modelling revealed that people with more nature experiences in childhood and higher satisfaction of neighbourhood coasts and rivers visited urban blue spaces more frequently. In addition, those who lived with pre‐school and primary school children also visited urban blue spaces more frequently than those without, likely for letting them play in blue spaces. These people primarily visited them to decrease their stress and to maintain their health by contacting with nature while keeping social distance to avoid being infected. Moreover, the visitation purpose and motivation partly differed between the coastal and river areas, which could be explained by the accessibility to and perception of blue spaces for urban people.The present study implies that, as well as green spaces, blue spaces provided places that people in urban areas could use to mitigate their stress and disorder during the pandemic. Our findings underpin the necessity of preserving both of them in urban planning for further benefits relating to health and well‐being. Read the free Plain Language Summary for this article on the Journal blog. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

In Japan, several local strong winds that are unique to a particular region are known by names such as "oroshi," "dashi," and "kaze," including Akagi‐oroshi and Kiyokawa‐dashi. In the area around Kobe City, northerly downslope winds from Mt. Rokko, or "Rokko‐oroshi," blow. However, there have not been many studies on Rokko‐oroshi, and its nature is not yet fully known. In particular, the nature of Rokko‐oroshi in the middle of Mt. Rokko (34.7321°N, 135.2539°E) and temperature changes induced by the blow of Rokko‐oroshi have not been studied so far. For example, during the blowing of Rokko‐oroshi, wind speeds up to 12 m/s can be recorded at the downwind while experiencing a rapid temperature decrease of between 5 and 8°C. In this study, winds and temperatures in the middle of Mt. Rokko were observed to investigate the characteristics and temperature reduction effect of Rokko‐oroshi. First, characteristics of wind speed and direction in the middle of Mt. Rokko were clarified to determine the intensity and duration in which Rokko‐oroshi blew. Second, hourly changes in temperature, wind speed, and wind direction were analyzed to relate variations in wind speed and direction with temperature reductions upwind and downwind of Mt. Rokko and within Kobe City. Lastly, radiosonde measurements upwind and downwind of Mt. Rokko were inspected to elucidate the physical mechanisms necessary for the generation of Rokko‐oroshi. [ABSTRACT FROM AUTHOR]

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Please cite this paper as: Ninomiya-Mori et al. (2010) Genetic evidence for containment of viruses in the first outbreak of influenza A pandemic (H1N1) 2009 in Kobe, Japan. Influenza and Other Respiratory Viruses Doi: 10.1111/j.1750-2659.2010.00188.x. On 16 May 2009, a high school student in Kobe with no history of overseas travel was reported as the first case of influenza A pandemic (H1N1) 2009 virus infection in Japan. Subsequently, it was revealed that the infection had spread to some cities in the Kansai region and most patients were high school students. The number of patients decreased rapidly within a week; however, it began to increase in the middle of July. We phylogenetically analyzed viral characteristics using 27 viruses isolated from patients living in Kobe. We demonstrated that viruses isolated in the early phase of the outbreak were distinguishable from those after the reappearance of patients. These findings provide genetic evidence for the effectiveness of public health containment measures in the Kansai region in preventing the progression of the outbreak. [ABSTRACT FROM AUTHOR]

The article offers information on several events including the 87th Congress of the Japan Gastroenterological Endoscopy Society at the Fukuoka International Congress Center in Japan from May 15-17, 2014, the Third Kobe International Endoscopy Hands-on Seminar Advance Course for Endoscopic Submucosal Dissection (ESD) at the Kobe Medical Device Development Center in Kobe from May 30 to June 1, and the 88th Congress of the Japan Gastroenterological Endoscopy Society in Japan from October 23-26.

This study, based on a questionnaire survey and workshops, and with a focus on the impact of an earthquake on the Nagata Elementary School Community in Kobe City, Japan, develops a collaborative model to assess the allocation of residents to shelters. The current official allocation plan is compared with three alternative allocations developed within the framework of this model. The collaborative model identifies accessibility, amenity, capacity, connectivity, continuity, security, and stability as the basic, necessary criteria for shelter planning. The three alternative allocations are very similar to the local residents' own choice of shelters, but they are quite different from the current official allocation plan, which is supposed to be followed but has achieved relatively low satisfaction among households. The proposed collaborative approach provides an effective tool to assess the officially determined allocation plan by taking into account the viewpoints of local residents, and the results are useful for enhancing community evacuation planning. [ABSTRACT FROM AUTHOR]

Aims: In order for hospitals to work efficiently in a pandemic, it is important to know how a pandemic affects the hospital staff. The aim of the present study was to investigate the psychological impact of the pandemic (H1N1) 2009 on hospital workers and how it was affected by the characteristics of the hospital, gender, age, job and work environment. Methods: In late June 2009, soon after the pandemic had ended in Kobe city, Japan, a questionnaire was distributed consisting of questions on sociodemographic characteristics, 19 stress-related questions and the Impact of Event Scale (IES) to all 3635 employees at three core general hospitals in Kobe. Exploratory factor analysis was applied to the 19 stress-related questions, and this produced four factors for evaluation (anxiety about infection, exhaustion, workload, and feeling of being protected). Multiple regression models were used to evaluate the association of personal characteristics with each score of the four factors and the IES. Results: Valid answers were received from 1625 employees. Workers at a hospital with intense liaison psychiatric services felt less psychological impact. Workers at a hospital that provided staff with information about the pandemic less frequently, felt unprotected. Workers in work environments that had a high risk of infection felt more anxious and more exhausted. The total IES score was higher in workers in high-risk work environments. Conclusions: It is important for hospitals to protect hospital workers during a pandemic and to rapidly share information about the pandemic. Liaison psychiatric services can help to reduce the impact of the pandemic on hospital workers. [ABSTRACT FROM AUTHOR]

Abstract The 1995 Kobe (Hyogo-ken Nanbu) earthquake (MJMA 7.2, Mw 6.9) occurred on Jan. 17, 1995, at a depth of 17 km, beneath the areas of southern part of Hyogo prefecture and Awaji Island. To investigate P-wave velocity distribution and seismological characteristics in the aftershock area of this great earthquake, a wide-angle and refraction seismic exploration was carried out by the Research Group for Explosion Seismology (RGES). The profile including 6 shot points and 205 observations was 135 km in length, extending from Keihoku, Northern Kyoto prefecture, through Kobe, to Seidan on Awaji Island. The charge of each shot was 350–700 kg. The P-wave velocity structure model showed a complicated sedimentary layer which is shallower than 2.5 km, a 2.5 km-thick basement layer whose velocity is 5.5 km/s, overlying the crystalline upper crust, and the boundary between the upper and lower crust. Almost all aftershock hypocenters were located in the upper crust. However, the structure model suggests that the hypocenters of the main shock and some aftershock clusters were situated deeper than the boundary between the upper and lower crust. We found that the P-velocity in the upper crust beneath the northern part of Awaji Island is 5.64 km/s which is 3% lower than that of the surrounding area. The low-velocity zone coincides with the region where the high stress moment release was observed. [ABSTRACT FROM AUTHOR]

Abstract The 1995 Hyogo-ken Nanbu (Kobe) earthquake, M7.2, occurred along the north-east–south-west trending Rokko–Awaji Fault system. Three boreholes of 1001 m, 1313 m and 1838 m deep were drilled in the vicinity of the epicenter of the earthquake. Each borehole is located at characteristic sites in relation to active faults and the aftershock distribution. In particular, the Nojima–Hirabayashi borehole [Hirabayashi National Research Institute for Earth Science and Disaster Prevention (NIED) drilling] in Awaji Island was drilled to a depth of 1838 m, approximately 320 m southeast from the surface rupture of the Nojima Fault, and it crosses fracture zones below a depth of 1140 m. In situ stress measurements by the hydraulic fracturing method were conducted in these boreholes within 1.5 years after the earthquake. Measurement results suggest the following: (i) Differential stress values are very small, approximately 10 MPa at a depth of 1000 m at each site; (ii) the orientation of maximum horizontal compression is almost the same in the boreholes, perpendicular to the surface trace of the faults, north-west–south-east; (iii) fault types estimated from the state of stress differ among these sites; and (iv) the differential stress value just beneath the fault fracture zone decreases abruptly to one-half of that above the fault zone in the Hirabayashi NIED drilling. These features support the idea that the shear stress along the Rokko–Awaji Fault system decreased to a low level just after the earthquake. [ABSTRACT FROM AUTHOR]

Abstract The Nojima Fault in Awaji, Hyogo prefecture, Japan, was ruptured during the 1995 Hyogo-ken Nanbu earthquake (MJMA = 7.2). Toshima is located close to the fault segment, in which a large dislocation has been observed on the Earth’s surface. Ikuha is near the southern end of the buried fault that extends from the surface rupture. Stresses are measured on core samples taken at depths of 310 m, 312 m and 415 m at Toshima and a depth of 351 m at Ikuha. The measured stresses show that both sites are in the field of a strike–slip regime, but compression dominates at Toshima. Defining the relative shear stress as the maximum shear stress divided by the normal stress on the maximum shear plane, the relative shear stress ranges from 0.42 to 0.54 at Toshima and is approximately 0.32 at Ikuha. While the value at Ikuha is moderate, those at Toshima are comparably large to those in areas close to the inferred fault of the 1984 Nagano-ken Seibu earthquake. Value amounts greater than 0.4 suggest that there are areas of large relative shear stress along faults, thus having the potential to generate earthquakes. Provided that the cores are correctly oriented, the largest horizontal stresses at shallow depths are in the direction from N113°E to N139°E at Toshima and N74°E at Ikuha, indicating that the fault does not orient optimally for the stress field at both sites. The slip is known to be predominant in the right-lateral strike–slip component. Although this slip may appear contradictory to the stress field at Toshima, the slip direction is found to be parallel to the measured stresses resolved on the fault plane for the first approximation. The ratio of shear stress to normal stress on the fault plane is roughly estimated to be greater than zero and smaller than 0.3 near Toshima. [ABSTRACT FROM AUTHOR]

Abstract An 800 m borehole was drilled near the Nojima Fault, on which a strike–slip larger then 1 m occurred during the 1995 Hyogo-ken Nanbu earthquake (M = 7.2). Crustal activity near the fault has been observed since May 1996 using a multicomponent instrument installed at the bottom of the borehole. Data of three components of strain, two components of tilt and temperature observed from May 1996 to December 1998 were analyzed. Long-term changes of strain and tilt show a north-east–south-west extension and southwards subsidence. As for the Earth tides and atmospheric effect, orientation of the principal axis of strain was mainly east-west and orientation of the maximum subsidence was mainly north-south. The observational data of strain had variations corresponding to a change in temperature at a depth of 800 m. The thermal expansion coefficient of the crust was calculated to be approximately 2.0 × 10-6/°K. [ABSTRACT FROM AUTHOR]

Abstract Distinctive fault ruptures, the Nojima Fault and Ogura Fault, appeared along the northwestern coast of Awaji Island at the time of the 1995 Hyogo-ken Nanbu earthquake (Kobe earthquake). In order to delineate the shallow resistivity structures around the faults just after they formed, Very Low Frequency Magnetotelluric (VLF-MT) surveys were made at five sites along the Nojima Fault and at one site along the Ogura Fault. Fourteen transects were made at the one site on the Ogura Fault, and another transect covers the area between the two faults. Changes in apparent resistivity or phase, or both, commonly occur when crossing the surface location of one of the faults, except for the northern transects at OGR-0 on the Ogura Fault. Apparent resistivity values of less than 100 Ωm were observed for Tertiary and Quaternary sediments and values larger than 200 Ωm for granitic rocks. The resistivity structures are related to the morphological characteristics of the fault ruptures. Remarkably conductive zones (less than 10 Ωm in apparent resistivity and 30–40 m in width) were found where the surface displacement is distinct and prominent along a single fault plane. If remarkably conductive zones were formed at the time of the 1995 Hyogo-ken Nanbu earthquake, the results provide a good constraint on the dimensions of a conductive zone near the surface that was made by one earthquake. Alternatively, if characteristic resistivity structures existed prior to the earthquake, the conductive zone was probably formed by some tens of earthquakes in relatively modern times. In this case, this phenomenon is inferred to be a concentration of fracturing in a narrow zone and is associated with the formation of clay minerals, which enhance rock conductivity. [ABSTRACT FROM AUTHOR]

Abstract In situ stress was measured close to the fault associated with the 1995 Kobe Earthquake (Hyogo-ken Nanbu earthquake; January 1995; M7.2) using the hydraulic fracturing method. The measurements were made approximately 2 years after the earthquake. The measured points were approximately 40 m from the fault plane at depths of about 1500 m. The maximum and the minimum horizontal compressive stresses were 45 MPa and 31 MPa, respectively. The maximum compressive stress and the maximum shear stress are very small in comparison with those of other seismically active areas. The azimuth of the maximum horizontal compressive stress was estimated from the observed azimuths of well bore breakouts at depths between 1400 m and 1600 m and was found to be N135° (clockwise). The maximum stress axis is perpendicular to the fault strike, N45°. These features are interpreted in terms of a small frictional coefficient of the fault. The shear stress on the fault was released and dropped almost to zero during the earthquake and it has not yet recovered. Zero shear stress on the fault plane resulted from the perpendicular orientation of one of the principal stress to the fault plane. [ABSTRACT FROM AUTHOR]

Abstract The temporal variation of seismic velocity near the Nojima Fault, which ruptured during the 1995 Kobe earthquake (Hyogo-ken Nanbu earthquake), was detected using an accurately controlled routine-operated seismic source (ACROSS). The source generates elastic waves by a centrifugal force of an eccentric mass rotating around an axis. The mass is driven with an AC servomotor whose angular position is accurately controlled with reference to a very accurate global positioning system (GPS) clock. The error of the mass’ position is less than 0.002 radian and does not accumulate. As a result, the source generates sinusoidal waves of very narrow spectral peaks enabling their detection with an excellent signal-to-noise ratio. Although the stability of the rotation is quite excellent, a large daily variation was found, which seems to be caused by changes in atmospheric temperature. The daily variation was 10% in amplitude and 0.1 radian in phase of the signal observed at the 800 m borehole seismometer. A significant variation was found to be due to that of coupling between the rotational source and the foundation made of reinforced concrete in which the source was situated. In order to make a correction on the signal of the 800 m borehole seismometer, the vibration of the foundation was measured and modeled assuming a rigid body movement. The correction successfully reduced the daily variation by approximately 90%, resulting in a variation of 1% in amplitude and 0.01 radian in phase. The phase variation of 0.01 radian corresponds to 100 μs and less than 0.1% in velocity over 1000 m between the source and the receiver. [ABSTRACT FROM AUTHOR]