Combined use of repeated active shots and ambient noise to detect temporal changes in seismic velocity: application to Sakurajima volcano, Japan

Additional file 1. Comparison of the results of coda-wave interferometry and seismic interferometry on the almost identical wave paths. Gray dots in top two panels are daily dv/v values obtained from seismic interferometry. The dv/v values obtained from coda-wave interferometry are shown by red squares and are overwritten assuming that the results for the 2012 experiment are the same as those on the same day from seismic interferometry. Error bars show Âą one standard deviation. Spatial distribution of three seismometers (squares) and a shot point (star) used in top two panels is shown in the bottom panel with black letters and red letters, respectively

Single-station cross-correlation analysis of ambient seismic noise: application to stations in the surroundings of the 2008 Iwate-Miyagi Nairiku earthquake

We introduce the single-station cross-correlation (SC) technique of processing ambient seismic noise and compare its results with the established cross-correlation (CC) and autocorrelation (AC) techniques. While CC is the correlation of the signals of two seismic stations with each other and AC is the correlation of a signal with itself, SC is the correlation of two different components of a single three-component seismic sensor. The comparison of the three different correlation techniques shows that CCs give the best results at frequencies below 0.5 Hz and that SCs give the best results at higher frequencies. In all three processing techniques, ambient seismic noise is correlated in order to reconstruct the Green's function describing the wave propagation between the first and the second sensor. By relating the coda parts of the daily Green's functions with the long-term reference Green's functions, shear wave velocity changes are determined. Here, we apply this technique to the data of 20 seismic stations in the surroundings of the fault zone of the Iwate-Miyagi Nairiku earthquake (MW=6.9), which occurred on 2008 June 13, UTC (2008 June 14, Japan Standard Time) in the northern part of the Japanese island Honshu. The data range from 2008 January to 2011 June and therefore include the Tohoku earthquake (MW=9.0), which occurred on 2011 March 11, off the coast of northern Honshu. The data are analysed in five different frequency ranges between 0.125 and 4.0 Hz. The data show coseismic velocity changes for both earthquakes followed by a post-seismic velocity recovery. In general, the coseismic velocity changes increase with frequency. For the Iwate-Miyagi Nairiku earthquake, the strongest velocity changes occur close to the fault zone. Quickly recovering coseismic velocity changes can be separated from changes not recovering during the study period. For the Tohoku earthquake, the complete area is affected by coseismic velocity changes. A modelling of the depth of the coseismic velocity changes indicates that the Iwate-Miyagi Nairiku earthquake can be explained either by large shallow velocity changes or by small, but deep changes. For one station, the observations can only be explained by assuming deeper changes. For the Tohoku earthquake, the modelling shows that different parts of the study area are affected in different ways, some showing shallow changes, others deeper changes. Furthermore, seasonal velocity variations occur, which are compatible for the different stations above 0.5 Hz, with velocity maxima in autum

Study on Erosion Factors Affecting Kuroboku Soil Loss I. Water Permeability of Stratified Soil and Slope Gradient

The authors examined the factors of bed soil affecting the loss of surface soil and the effects of these factors on the extent of the soil loss. They conducted a multivariate analysis using actual measurement value at a laboratory erosion experiment. They also conducted a simulation of erosion in soil loss using the bed soil factors. Soil loss quantity is dependent on the coefficient of permeability of bed soil; the steeper the latter is, the more the former increases. Lateral soil scattering quantity is not much affected with the permeability of bed soil, nor with the gradient of a slope. When the slope gradient of bed soil is equal, soil loss quantity is affected with the coefficient of permeability and the ignition loss of the bed soil. On the otherhand , when the slope gradient of bed soil is different, soil loss quantity is most affected with the slope gradient, followed by the coefficient of permeability of the bed soil

Breast Cancer with Cartilaginous and/or Osseous Metaplasia Diagnosed by Lymph Nodal Metastasis:A Case Report

Breast cancer with cartilaginous and/or osseous metaplasia is a type of metaplastic carcinomas and is a rare disease. We report the case of a 49 year-old female who underwent right mastectomy for a large breast tumor. Histological examinations revealed a mixed tumor with both stromal and epithelial elements;the stroma showed poor differentiated spindle-shape and multiform cells with a massive osseous matrix, and atypical epithelial cells, which mainly existed on the surface of the cysts, showed nucleic atypia. The tumor was diagnosed as a malignant phyllodes tumor with osteosarcomatous differentiation;it was not identified as a metaplastic carcinoma because of the lack of proof of a cancerous component. Two years after a mastectomy, swelling of the axillary lymph nodes was found and a biopsy was performed. Histological findings for the lymph node indicated a metastasis of the invasive ductal carcinoma. The primary tumor was re-examined and was considered to be the origin of the lymph nodal metastasis. Lymph nodal metastasis of cancer proved that the primary tumor had cancerous potential, and the pathological diagnosis was altered to a breast cancer with cartilaginous and/or osseous metaplasia.</p