Seismic Evidence of Pop-up Tectonics Beneath the Shillong Plateau Area of Northeast India

Our detailed analysis of high-quality arrival time data recorded by the local seismographic network using three-dimensional seismic tomography of the Shillong Plateau region using high-quality arrival times of the body wave phases recorded at a dense temporary seismic network. This technique is used to understand the heterogeneities of the crust and its implications for pop-up tectonics characterizing evaluation the of the Shillong Plateau. We investigated an area covering ~150 ×100 km2 that revealed seismicity to be confined in a depth range ≤ 60 km. High - velocity anomalies in the upper crust appear to be responsible for intense small to moderate seismic activity in the region. Crustal seismic velocities inferred from 3-D seismic tomography showed significant lateral heterogeneities beneath the lithosphere of the Shillong Plateau. High-velocity anomalies in the uppermost crust, interpreted as the Shillong Plateau act as a geometric asperity where interseismic strain may accumulate. Low-velocity anomalies in the lower crust probably play a major role to accommodating the stresses generated due to plate separation, culminating in future sources of great earthquakes. The geological faults are well imaged in the cross-sections and support the concept of Pop-up tectonics beneath the Shillong of NE India.

An exception to every rule; high velocity impact not always required for bilateral 1st rib fractures

Introduction First rib fractures are commonly reported in high velocity trauma. The neuromuscular sequelae that can ensue, not the physical disruption of the rib, necessitate thorough evaluation for such injuries. Methods We describe a case of a patient who sustained bilateral rib fractures following low-energy trauma.

Mechanism Elucidation of High-Pressure Generation in Cellular Metal at High-Velocity Impact

Cellular metals exhibit diverse properties, depending on their geometries and base materials. This study investigated the mechanism of high-pressure generation during the high-velocity impact of unidirectional cellular (UniPore) materials. Cubic UniPore copper samples were mounted on a projectile and subjected to impact loading using a powder gun to induce direct impact of samples. The specimens exhibited a unique phenomenon of high-pressure generation near the pores during compression. We elucidate the mechanism of the high-pressure phenomenon and discuss the pore geometries that contribute to the generation of high pressures.

Contiguous-Level Unilateral Cervical Spine Facet Dislocation—A Report of a Less Discussed Subtype

Unilateral facet dislocation of subaxial cervical spine trauma is characterized by dislocation of inferior facet of superior vertebra over the superior facet of inferior vertebra. The injury is due to high-velocity trauma and associated with instability of spinal column. Such unilateral facet dislocations occurring at multiple adjacent levels for some reason are not reported or studied frequently. We have reported two cases of multiple-level dislocation of unilateral facets managed in our hospital with a review of available literature. The injury occurs as one side of the motion segment translates and rotates around an intact facet on the contralateral side. The major mechanism of injury is distractive flexion injury with axial rotation component. The injury is associated with instability secondary to loss of the discoligamentous complex. In cases with multiple-level dislocations of unilateral cervical facets, there are multiple mechanisms associated with significant neurological injury and most of them succumb at the site of injury. Only three other cases are available in English language literature. The neurological outcome is invariably poor. Multiple-level facet dislocations of subaxial cervical spine are reported sparsely in literature. We suspect that due to high-velocity nature of these injuries, most of them succumb soon after injury and not often reported. This article reports two cases of contiguous-level unilateral facet dislocation of subaxial cervical spine with associated injuries and the outcomes with review of literature.

Analysis of propagation characteristics of Rayleigh surface acoustic waves on Yb0.33Al0.67N piezoelectric films/high-velocity substrates

Piezoelectricity of YbAlN films has recently been shown to be almost as high as that of ScAlN films. YbAlN film surface acoustic wave (SAW) resonators are expected to have a high coupling factor. We theoretically investigated the propagation characteristics of first-mode Rayleigh SAWs (RSAWs) on Yb0.33Al0.67N film/high-velocity Si, sapphire, AlN, SiC, BN, and diamond substrates. The first-mode RSAWs on the YbAlN layered structures had high coupling factors, higher than those on ScAlN layered structures. An enhancement of the effective coupling factor of the first mode RSAWs was observed in polarity inverted YbAlN film/BN or diamond substrate structures.