Focal mechanisms and stress field in the Nobi fault area, central Japan Seismology

In this study, we obtained 728 focal mechanisms of small earthquakes with depths shallower than 20 km that occurred from May 2009 to May 2013 in the Nobi fault area in central Japan. The averages of the azimuths of the P- and T-axes were N97° ± 23° E and N6° ± 32° E, and the averages of the dips of the P- and T-axes were 11° ± 10° and 32° ± 25°, respectively. These variations in the P- and T-axes come from variation of the focal mechanisms; both strike-slip and reverse fault earthquakes were observed in the study area. A stress tensor inversion method was applied to the focal mechanisms, and we obtained and characterized the spatial pattern of the tectonic stress. We found that the maximum principal stress (σ 1) is oriented E-W over almost the entire study area. The stress ratio R, which is defined as R = (σ 1 - σ 2)/(σ 1 - σ 3), ranges from 0.65 to 0.98, and the average R over the entire study area is 0.82. The average stress ratio is close to unity, indicating σ 2 ≈ σ 3, and thus the dominant stress in this region is a uniaxial compression in the direction of σ 1. The direction of the σ 1-axis fluctuates locally at the southeastern end of the seismic fault ruptured by the 1891 Nobi earthquake. This fluctuation is limited to within a very narrow zone across the seismic fault in the upper crust shallower than approximately 10 km, suggesting that most of the deviatoric stress at the southeastern end of the seismic fault ruptured by the 1891 Nobi earthquake was not released

Focal mechanisms and stress field in the Nobi fault area, central Japan

In this study, we obtained 728 focal mechanisms of small earthquakes with depths shallower than 20 km that occurred from May 2009 to May 2013 in the Nobi fault area in central Japan. The averages of the azimuths of the P- and T-axes were N97 degrees +/- 23 degrees E and N6 degrees +/- 32 degrees E, and the averages of the dips of the P- and T-axes were 11 degrees +/- 10 degrees and 32 degrees +/- 25 degrees, respectively. These variations in the P- and T-axes come from variation of the focal mechanisms; both strike-slip and reverse fault earthquakes were observed in the study area. A stress tensor inversion method was applied to the focal mechanisms, and we obtained and characterized the spatial pattern of the tectonic stress. We found that the maximum principal stress (sigma(1)) is oriented E-W over almost the entire study area. The stress ratio R, which is defined as R = (sigma(1) - sigma(2))/(sigma(1) - sigma(3)), ranges from 0.65 to 0.98, and the average R over the entire study area is 0.82. The average stress ratio is close to unity, indicating sigma(2) approximate to sigma(3), and thus the dominant stress in this region is a uniaxial compression in the direction of sigma(1). The direction of the sigma(1)-axis fluctuates locally at the southeastern end of the seismic fault ruptured by the 1891 Nobi earthquake. This fluctuation is limited to within a very narrow zone across the seismic fault in the upper crust shallower than approximately 10 km, suggesting that most of the deviatoric stress at the southeastern end of the seismic fault ruptured by the 1891 Nobi earthquake was not released

A modified multi-patch technique for double-layered repair of ischemic posterior ventricular septal rupture

Abstract Background The rupture of the posterior ventricular septum after acute inferior myocardial infarction is more challenging to repair than ruptures in other sites since it is less accessible and anatomically restricted. We described a modification of Daggett’s original technique of multi-patch repair of ruptured posterior septum. Case presentation The technique was employed in the operation of a 67-year-old male who presented with severe heart failure at the 10th day after he developed inferior myocardial infarction. His ventricular septum had ruptured at the level between the posteromedial papillary muscle and the mitral annulus. A large endoventricular patch covered separately over the locally patched septal defect and the ventriculotomy defect which was going to be roofed eventually with an external patch. Both defects were then individually closed in double layers, holding a single continuous patch in common. The common use of a single patch expedited multilayered closure of the left ventricular defects and could minimize geometric remodeling of the covered area. The patches on both the endocardial and the epicardial sides avoided potentially fatal bleeding from the ventriculotomy site. The transmural mattress sutures incorporating ventriculotomy patches required minimal bites toward the posteromedial papillary muscle and mitral annulus, thereby preserving the mitral valve function. Conclusions Thus, the technique enhances the advantage of the left ventriculotomy in the repair of posterior septal rupture and avoids ventriculotomy-related morbidity

Repetitive complications after prosthetic graft for inflammatory aortic aneurysm

The presence of retroperitoneal fibrosis after an aortic graft replacement is a marker of poor prognosis following aortic graft replacement. Herein we report the case of a 39-year-old man with retroperitoneal fibrosis that had been causing ureteral obstruction. The man had undergone repeated aortic graft replacement due to bacteremia and aortic graft–small intestinal fistula that occurred 4 years after initial aortic grafting for an inflammatory aortic aneurysm. The patient was discharged after 4 weeks of intravenous antibiotic therapy following the latest aortic graft replacement