Large anomalous Nernst effect and nodal plane in an iron-based kagome ferromagnet

Kagome ferromagnet Fe 3 Sn exhibits large magnetic thermoelectric effect due to Berry curvature enhanced by a nodal plane.

THE HINDU KUSH EARTHQUAKE on October 26, 2015 with Mw=7.5, I0~7: PRELIMINARY SEISMICITY and AFTERSHOCK SEQUENCE

On October 26, 2015, a strong Hindu Kush earthquake with KR=17.0, Mw=7.5 occurred in the Afghan Pamir-Hindu Kush subzone at a depth of hpP=217 km. Shakes of varying intensity caused by this earthquake were recorded in settlements of 14 states: Afghanistan, Tajikistan, Pakistan, Turkmenistan, India, Kyrgyzstan, Uzbekistan, Kazakhstan, China, Iran, Nepal, United Arab Emirates, Russia, Qatar and Bangladesh with a total area of S=14106 km2. The earthquake was preceded by three large (KR=12.5, 12.1, 14.0) foreshocks and was accompanied by a series of more than 1400 aftershocks unprecedented for aftershocks of deep earthquakes with KR=9–13. The energy step between the mainshock and the maximum foreshock is Kfor=3.0, between the mainshock and the maximum (KR=12.8) aftershock – Kaft=4.2. The aftershock recurrence graph has a slope =–0.67, which in absolute value is higher than the average value in the region =0.50. The attenuation para-meter  of the Omori law in the initial phase of attenuation, =–1.26, in absolute value is also higher than the average =1.0 for strong earthquakes in the World. Based on the results of a joint analysis of the focal me-chanism solutions of different agencies and vertical sections along and across the aftershock cloud, it was con-cluded that an upthrust movement occurred in the source along a steep east-south-east nodal plane, dipping to the south. The reason for the activity at the site of the earthquake is the movement of the Indian continent to the north and its collision with Eurasia, as a result of which the separation and subduction of the Hindu Kush plate continue. The Hindu Kush earthquake on October 26, 2015, and its aftershocks are just one of the events of successive deformation and stress relief in the latitudinal zone, marked in 2015 by the migration of earthquake epicenters with KR=13–17 from east to west.

Microseismicity in the central Southern Alps, Westland, New Zealand

<p>Present-day seismicity associated with the central Alpine Fault and the zone of active deformation and rock uplift in the central Southern Alps is reported in this thesis. Robust hypocentre locations and magnitude estimates for ~2300 earthquakes have been obtained analysing 18 months of data from the Southern Alps Microearthquake Borehole Array (SAMBA), designed for this study. The earthquakes are distributed between the Alpine Fault and the Main Divide Fault zone and confined to shallow depths (90% of events ≤12.2 km). The thickness of the seismogenic zone follows lateral variations in crustal resistivity: earthquake hypocentres are restricted to depths where resistivities exceed 390 Ω m. Rocks at greater depth are interpreted to be too hot, too fluid-saturated, or too weak to produce detectable earthquakes. A low-seismicity zone extends between the Whataroa and Wanganui rivers at distances 15–30 km southeast of the fault, which is concluded to be a relatively strong, unfractured block that diverts deformation around it. A new magnitude scale is developed incorporating the effects of frequency-dependent attenuation, which enables magnitudes to be calculated consistently for earthquakes of different sizes and frequency contents. Focal mechanism solutions for 379 earthquakes exhibit predominantly strike-slip mechanisms. Inversion of these focal mechanisms to determine the prevailing tectonic stress field reveals a maximum horizontal compressive stress direction of 115±10°, consistent with findings from elsewhere in South Island. The 60° angle between the strike of the Alpine Fault and the direction of maximum horizontal compressive stress suggests that the Alpine Fault is poorly oriented in an Andersonian sense. Earthquake swarms of at least 10 events with similar waveforms frequently occur within the region, of which some were remotely triggered by two major South Island earthquakes. Focal mechanisms of the largest event in each swarm (ML≤2.8) reveal at least one steeply-dipping nodal plane (≥50°) and one well-oriented nodal plane in the tectonic stress field. The swarms exhibit a distinctly different inter-event time versus duration pattern from that of typical mainshock-aftershock sequences. The triggered seismicity commences with the passage of the surface waves, continues for ~5 and ~2 days, and is followed by a quiescence period of approximately equal length. Remotely triggered swarms occur delayed by several hours and their delay and locations are consistent with fluid diffusion from a shallow fluid reservoir. Estimated peak dynamic stresses (≥0.09 MPa) imposed by the surface waves are comparable to observations of triggering thresholds (>0.01 MPa) elsewhere. The triggered swarms have no apparent differences from the background swarms, and appear to have been clock-advanced. Tectonic tremor in the vicinity of the Alpine Fault coincides with a low-velocity, high-attenuation zone at depth. The tremor occurs at the downdip extension of the Alpine Fault and in the region where bending of the Australian and Pacific plates is largest at depths spanning 12–49 km. Similarities with tremor occurring on the San Andreas Fault near Cholame in terms of tremor duration, depth, spatial extent and amplitude distribution, imply property variations in the lower crust and upper mantle along the strike of the Alpine Fault.</p>

Microseismicity in the central Southern Alps, Westland, New Zealand

<p>Present-day seismicity associated with the central Alpine Fault and the zone of active deformation and rock uplift in the central Southern Alps is reported in this thesis. Robust hypocentre locations and magnitude estimates for ~2300 earthquakes have been obtained analysing 18 months of data from the Southern Alps Microearthquake Borehole Array (SAMBA), designed for this study. The earthquakes are distributed between the Alpine Fault and the Main Divide Fault zone and confined to shallow depths (90% of events ≤12.2 km). The thickness of the seismogenic zone follows lateral variations in crustal resistivity: earthquake hypocentres are restricted to depths where resistivities exceed 390 Ω m. Rocks at greater depth are interpreted to be too hot, too fluid-saturated, or too weak to produce detectable earthquakes. A low-seismicity zone extends between the Whataroa and Wanganui rivers at distances 15–30 km southeast of the fault, which is concluded to be a relatively strong, unfractured block that diverts deformation around it. A new magnitude scale is developed incorporating the effects of frequency-dependent attenuation, which enables magnitudes to be calculated consistently for earthquakes of different sizes and frequency contents. Focal mechanism solutions for 379 earthquakes exhibit predominantly strike-slip mechanisms. Inversion of these focal mechanisms to determine the prevailing tectonic stress field reveals a maximum horizontal compressive stress direction of 115±10°, consistent with findings from elsewhere in South Island. The 60° angle between the strike of the Alpine Fault and the direction of maximum horizontal compressive stress suggests that the Alpine Fault is poorly oriented in an Andersonian sense. Earthquake swarms of at least 10 events with similar waveforms frequently occur within the region, of which some were remotely triggered by two major South Island earthquakes. Focal mechanisms of the largest event in each swarm (ML≤2.8) reveal at least one steeply-dipping nodal plane (≥50°) and one well-oriented nodal plane in the tectonic stress field. The swarms exhibit a distinctly different inter-event time versus duration pattern from that of typical mainshock-aftershock sequences. The triggered seismicity commences with the passage of the surface waves, continues for ~5 and ~2 days, and is followed by a quiescence period of approximately equal length. Remotely triggered swarms occur delayed by several hours and their delay and locations are consistent with fluid diffusion from a shallow fluid reservoir. Estimated peak dynamic stresses (≥0.09 MPa) imposed by the surface waves are comparable to observations of triggering thresholds (>0.01 MPa) elsewhere. The triggered swarms have no apparent differences from the background swarms, and appear to have been clock-advanced. Tectonic tremor in the vicinity of the Alpine Fault coincides with a low-velocity, high-attenuation zone at depth. The tremor occurs at the downdip extension of the Alpine Fault and in the region where bending of the Australian and Pacific plates is largest at depths spanning 12–49 km. Similarities with tremor occurring on the San Andreas Fault near Cholame in terms of tremor duration, depth, spatial extent and amplitude distribution, imply property variations in the lower crust and upper mantle along the strike of the Alpine Fault.</p>

Numerical and experimental analysis of a hybrid material acoustophoretic device for manipulation of microparticles

Acoustophoretic microfluidic devices have been developed for accurate, label-free, contactless, and non-invasive manipulation of bioparticles in different biofluids. However, their widespread application is limited due to the need for the use of high quality microchannels made of materials with high specific acoustic impedances relative to the fluid (e.g., silicon or glass with small damping coefficient), manufactured by complex and expensive microfabrication processes. Soft polymers with a lower fabrication cost have been introduced to address the challenges of silicon- or glass-based acoustophoretic microfluidic systems. However, due to their small acoustic impedance, their efficacy for particle manipulation is shown to be limited. Here, we developed a new acoustophoretic microfluid system fabricated by a hybrid sound-hard (aluminum) and sound-soft (polydimethylsiloxane polymer) material. The performance of this hybrid device for manipulation of bead particles and cells was compared to the acoustophoretic devices made of acoustically hard materials. The results show that particles and cells in the hybrid material microchannel travel to a nodal plane with a much smaller energy density than conventional acoustic-hard devices but greater than polymeric microfluidic chips. Against conventional acoustic-hard chips, the nodal line in the hybrid microchannel could be easily tuned to be placed in an off-center position by changing the frequency, effective for particle separation from a host fluid in parallel flow stream models. It is also shown that the hybrid acoustophoretic device deals with smaller temperature rise which is safer for the actuation of bioparticles. This new device eliminates the limitations of each sound-soft and sound-hard materials in terms of cost, adjusting the position of nodal plane, temperature rise, fragility, production cost and disposability, making it desirable for developing the next generation of economically viable acoustophoretic products for ultrasound particle manipulation in bioengineering applications.

The M 6.5 Ambon earthquake 26 September 2019: the source mechanism and the aftershock sequence characteristics

The area of Ambon, Maluku is located in the subduction zone in bands where the Australian plate meets the Eurasian plate, thus causing tectonic activities. The Ambon earthquake on 26th September 2019 with 6.5 Magnitude, while the Epicentral coordinates of the earthquake were determined as 3,53° S and 128,39° E and a focal depth of 10 km, according to the Agency for Meteorology Climatology and Geophysics, Indonesia. This earthquake was strongly felt at the biggest shock was felt with intensity VI-VII as unified in Ambon City, while several other areas are reported to have experienced small shaking, such as Intensity V in Masohi, and Intensity IV in Namlea and Namrole. We used a dataset of 24 waveforms of seven sensors, we determine a tabular solution, which have a large moment of 0.4573 x 1019 N-m, the depth is 6 km by minimizing the inversion residual. The method resulting strike and rake fault, with strike: 341.8°; dip; 81.5°; rake: 158.4°, and second nodal plane strike: 75.1°; dip; 68.6°; rake: 9.14°. The mechanisms were compared with those from other agency in agreement. The time decay intervals between mainshocks and significant aftershocks follow Mogi and Utsu’s Law but with a relatively faster rate of decay than that of aftershocks in general.

Seismicity around Cirata Dam, West Java, Indonesia based on BMKG local seismic network

The addition of seismic stations to the seismic network of BMKG in 2019 has successfully located some local earthquakes. In the early 2020 occurred significant earthquakes around Cirata Dam, West Java. During a period of January-March 2020, there have been 5 earthquakes with magnitude ranging from 1.8-3.7. Those earthquakes caused ground shaking up to III MMI intensity scale around the epicenters area. The relocation of the hypocenter using the Teletomo-DD method is applied in this study so that the data can be interpreted to show the fault geometry in this area. The relocated epicenters distribute in the east side of the dam elongated in SSW-NNE direction. Vertical distribution of relocated hypocenters show that the earthquake occurred at 1.1 km down to 14.5 km depth. Hypocenter depths are getting deeper to the north direction, this suggest dip orientation of the fault plane. The reconstructed dip orientation is consistent with nodal plane resulted from moment tensor inversion results, that shown fault planes oriented in N 2290 –2720 E direction and dip 490–500 to the north direction.

Classification of Zagros earthquakes based on focal mechanism

The Zagros suture zone is seismically active region in Iranian plateau. This region is of high importance in terms of seismicity, since it is a vast and populated region and in recent years the earthquakes with high intensities have frequently occurred and have caused extensive destruction and heavy human loss. The study of the focal mechanism is very important in understanding the seismotectonic characteristics. Focal mechanisms of Zagros were collected over a period of 20 years and they were classified by FMC software. Seven groups were considered for the type of faulting and Zagros was divided into three zones. For each zone, the frequency percentage of each group of faults was determined. The most of faulting are of the reverse and compression type with the strike-slip component. Finally, the role of nodal plane selection in determining the type of faulting was discussed and it was found that the selection of each nodal plane in determining the type of faulting has the same result.