In recent years, predictions of damage from earthquakes have been made on a prefectural scale, and expectations exist that more detailed damage forecasts should be made even on a city/town/village scale. It is importa...In recent years, predictions of damage from earthquakes have been made on a prefectural scale, and expectations exist that more detailed damage forecasts should be made even on a city/town/village scale. It is important to know detailed ground characteristics to do damage prediction on a fine scale. Using GIS is the best way to communicate this planar disaster prevention information to the general public. Yokohama City is the second largest city in Japan and developed as part of the capital region of Metropolitan Tokyo. Recently, the population of this city has reached about 3,000,000, and economic and cultural facilities, social infrastructure, and residential complexes are concentrated in this city. The capital region, including Yokohama City, was attacked by the 1923 Great Kanto Earthquake (M7.9) and Yokohama City was devastated by this earthquake. From the research so far, it is known that the H/V spectrum obtained from microtremor observation has a good correlation with the ground characteristics. The authors have been conducting high-density tremor observations that have been ongoing since the 1990s, mainly in Kanagawa Prefecture, Japan. Here, we have organized the predominant periods obtained from the observation results for Yokohama City. The entirety of Yokohama City was divided into 250 m × 250 m meshes and their centers were used as microtremor observation sites. Excluding sites that could not be used due to geographical conditions, observations were made at approximately 5700 sites. So, we compared the data obtained separately, such as the period, terrain classification, and amplification characteristics. The distribution maps of predominant periods in Yokohama City show that the city contains a lot of artificially transformed land, and consequently, the distribution of predominant periods is not uniform. However, it can be seen that the periods become gradually longer, moving from the higher elevation eastern part toward the lower elevation western part. Investigation of the site amplification facto展开更多
Micromotion is the daily tiny vibration of the earth</span><span style="font-family:Verdana;">’</span><span style="font-family:Verdana;">s surface. Micromotional exploratio...Micromotion is the daily tiny vibration of the earth</span><span style="font-family:Verdana;">’</span><span style="font-family:Verdana;">s surface. Micromotional exploration can use the surface wave information of micro motion to study the shallow structure of underground media. In this study, we collected microtremor data at 68 stations in the Middle-Lower Yangtze Metallogenic Belt (MLYMB) and determined the resonant frequency and obtained the distribution of sedimentary thickness in this area by using H/V spectral ratio. According to the results of H/V, the sedimentary layer in the basin is thick, and the predominant frequency of the basin is 0.05</span><span style="font-family:""> </span><span style="font-family:Verdana;">-</span><span style="font-family:""> </span><span style="font-family:Verdana;">0.1</span><span style="font-family:""> </span><span style="font-family:Verdana;">Hz. There are no obvious lateral changes in the impedance interface between bedrock and sedimentary layer in this area. The basement of Tongling, Anqing and Luzhou mining areas and their adjacent areas is Kongling-Dongling type basement, which is composed of a set of metamorphic core complex. The predominant frequency is 0.05</span><span style="font-family:""> </span><span style="font-family:Verdana;">-</span><span style="font-family:""> </span><span style="font-family:Verdana;">0.1</span><span style="font-family:""> </span><span style="font-family:Verdana;">Hz. The sedimentary thickness gradually thinned from 3800</span><span style="font-family:""> </span><span style="font-family:Verdana;">m in the west to 2100</span><span style="font-family:""> </span><span style="font-family:Verdana;">m in the East. Moreover, this article used SPAC (spatial autocorrelation) method to obtain the S-wave velocity structure of the mining area near Luzong. The SPAC method reveals that the depth of the interface between the loose sediments and the volcanic rocks is about 600 m in the study area near the Luzhou mining area in the Middle-Lower Yangtze Met展开更多
文摘In recent years, predictions of damage from earthquakes have been made on a prefectural scale, and expectations exist that more detailed damage forecasts should be made even on a city/town/village scale. It is important to know detailed ground characteristics to do damage prediction on a fine scale. Using GIS is the best way to communicate this planar disaster prevention information to the general public. Yokohama City is the second largest city in Japan and developed as part of the capital region of Metropolitan Tokyo. Recently, the population of this city has reached about 3,000,000, and economic and cultural facilities, social infrastructure, and residential complexes are concentrated in this city. The capital region, including Yokohama City, was attacked by the 1923 Great Kanto Earthquake (M7.9) and Yokohama City was devastated by this earthquake. From the research so far, it is known that the H/V spectrum obtained from microtremor observation has a good correlation with the ground characteristics. The authors have been conducting high-density tremor observations that have been ongoing since the 1990s, mainly in Kanagawa Prefecture, Japan. Here, we have organized the predominant periods obtained from the observation results for Yokohama City. The entirety of Yokohama City was divided into 250 m × 250 m meshes and their centers were used as microtremor observation sites. Excluding sites that could not be used due to geographical conditions, observations were made at approximately 5700 sites. So, we compared the data obtained separately, such as the period, terrain classification, and amplification characteristics. The distribution maps of predominant periods in Yokohama City show that the city contains a lot of artificially transformed land, and consequently, the distribution of predominant periods is not uniform. However, it can be seen that the periods become gradually longer, moving from the higher elevation eastern part toward the lower elevation western part. Investigation of the site amplification facto
文摘Micromotion is the daily tiny vibration of the earth</span><span style="font-family:Verdana;">’</span><span style="font-family:Verdana;">s surface. Micromotional exploration can use the surface wave information of micro motion to study the shallow structure of underground media. In this study, we collected microtremor data at 68 stations in the Middle-Lower Yangtze Metallogenic Belt (MLYMB) and determined the resonant frequency and obtained the distribution of sedimentary thickness in this area by using H/V spectral ratio. According to the results of H/V, the sedimentary layer in the basin is thick, and the predominant frequency of the basin is 0.05</span><span style="font-family:""> </span><span style="font-family:Verdana;">-</span><span style="font-family:""> </span><span style="font-family:Verdana;">0.1</span><span style="font-family:""> </span><span style="font-family:Verdana;">Hz. There are no obvious lateral changes in the impedance interface between bedrock and sedimentary layer in this area. The basement of Tongling, Anqing and Luzhou mining areas and their adjacent areas is Kongling-Dongling type basement, which is composed of a set of metamorphic core complex. The predominant frequency is 0.05</span><span style="font-family:""> </span><span style="font-family:Verdana;">-</span><span style="font-family:""> </span><span style="font-family:Verdana;">0.1</span><span style="font-family:""> </span><span style="font-family:Verdana;">Hz. The sedimentary thickness gradually thinned from 3800</span><span style="font-family:""> </span><span style="font-family:Verdana;">m in the west to 2100</span><span style="font-family:""> </span><span style="font-family:Verdana;">m in the East. Moreover, this article used SPAC (spatial autocorrelation) method to obtain the S-wave velocity structure of the mining area near Luzong. The SPAC method reveals that the depth of the interface between the loose sediments and the volcanic rocks is about 600 m in the study area near the Luzhou mining area in the Middle-Lower Yangtze Met
