Proximate and antinutritional assessments of stingrays

Stingrays are one of the marine fishes that inhabit the shallow part of the ocean. They are well known to the locals as cuisine and its parts as accessories for items such as handbags, belts, and decorations. Stingrays of species Himantura undulata and Maculabatis gerrardi are commonly caught by fishermen of Sarawak, but most of its nutritional and antinutritional factors both species are unknown. This study focused on the analysis of some proximate composition such as moisture, ash, and lipid content. Analysis of total organic matter was done as well. The stingrays were obtained from local fish market in Kuching, Sarawak. The method used for moisture (wet basis), ash, and total organic matter is of AOAC (method 930.15), while crude lipid content was based on the Chedoloh method of extraction. The study revealed that H. undulata and M. gerrardi are nutritious in terms of moisture, ash, and lipid content to be 78.44 and 80.74% (dry basis), 0.48 and 1.37%, 2.46 and 7.74% respectively.

Simulation of Density and Flow Dynamics in a Lagoon Aquifer Environment and Implications for Nutrient Delivery From Land to Sea

The near coastal zone, hosting the saltwater-freshwater interface, is an important zone that nutrients from terrestrial freshwaters have to pass to reach marine environments. This zone functions as a highly reactive biogeochemical reactor, for which nutrient cycling and budget is controlled by the water circulation within and across that interface. This study addresses the seasonal variation in water circulation, salinity pattern and the temporal seawater-freshwater exchange dynamics at the saltwater-wedge. This is achieved by linking geophysical exploration and numerical modeling to hydrochemical and hydraulic head observations from a lagoon site at the west coast of Denmark. The hydrochemical data from earlier studies suggests that increased inland recharge during winter drives a saltwater-wedge regression (seaward movement) whereas low recharge during summer causes a wedge transgression. Transient variable density model simulations reproduce only the hydraulic head dynamics in response to recharge dynamics, while the salinity distribution across the saltwater wedge cannot be reproduced with accuracy. A dynamic wedge is only simulated in the shallow part of the aquifer (<5 m), while the deeper parts are rather unaffected by fluctuations in freshwater inputs. Fluctuating salinity concentrations in the lagoon cause the development of a temporary intertidal salinity cell. This leads to a reversed density pattern in the underlying aquifer and the development of a freshwater containing discharge tube, which is confined by an overlying and underlying zone of saltwater. This process can explain observed trends in the in-situ data, despite an offset in absolute concentrations. Geophysical data indicates the presence of a deeper low hydraulic conductive unit, which coincides with the stagnant parts of the simulated saltwater-wedge. Thus, exchange fluxes refreshing the deeper low permeable areas are reduced. Consequently, this study suggests a very significant seasonal water circulation within the coastal aquifer near the seawater-freshwater interface, which is governed by the hydrogeological setting and the incoming freshwater fluxes, where nutrient delivery is limited to a small corridor of the shallow part of the aquifer.

Seismic Velocity Structure of the Shallow Part of the Alpine Fault and Gravity Study of the Basement Features in the Whataroa River Flood Plain, Central Westland, South Island

<p>The deep and middle sections of the Alpine fault have extensively been studied, however, the shallow part has had relatively minor geophysical attention. This study focuses on the basement geometry and the determination of the upper-crustal velocity structure of the Alpine fault in the vicinity of the Whataroa River flood plain in Central Westland, South Island. Data from a temporary gravity survey collected in November 2006, the GNS gravity database and four of the westernmost shot gathers from the SIGHT96's transect 1 were used for this project. A ray-tracing software was used to establish the velocity structure of the shallow part of the Alpine fault. Seismic velocities decrease to 3.8 km/s immediately southeast of the mylonite strip, which is adjacent to the Alpine fault's ramp heading towards the fault's surface trace from the southeast or from depth. Velocities of 5 km/s reach 2 km depth to the southeast of the Alpine fault's ramp. Results of the gravity and seismic models coincide in the positions and the dimensions of two northwest-orientated glacial overdeepings. The strike of their alignment is offset to the northeast by 3.5 km and is sub-parallel to the mouth of the Whataroa River. We propose that these kettle holes, thought to have been carved successively during the Waimea and Otira glaciations, are the beheaded river mouth of the Whataroa river. By supposing that the furthest kettle hole was carved during the Waimea glaciation, the 3.5 km offset thus corresponds to 140 Ka of dextral slip on the Alpine fault, we could approximate the mean displacement rate over the time interval of 140-18 Ka of 25 mm/yr.</p>

Seismic Velocity Structure of the Shallow Part of the Alpine Fault and Gravity Study of the Basement Features in the Whataroa River Flood Plain, Central Westland, South Island

<p>The deep and middle sections of the Alpine fault have extensively been studied, however, the shallow part has had relatively minor geophysical attention. This study focuses on the basement geometry and the determination of the upper-crustal velocity structure of the Alpine fault in the vicinity of the Whataroa River flood plain in Central Westland, South Island. Data from a temporary gravity survey collected in November 2006, the GNS gravity database and four of the westernmost shot gathers from the SIGHT96's transect 1 were used for this project. A ray-tracing software was used to establish the velocity structure of the shallow part of the Alpine fault. Seismic velocities decrease to 3.8 km/s immediately southeast of the mylonite strip, which is adjacent to the Alpine fault's ramp heading towards the fault's surface trace from the southeast or from depth. Velocities of 5 km/s reach 2 km depth to the southeast of the Alpine fault's ramp. Results of the gravity and seismic models coincide in the positions and the dimensions of two northwest-orientated glacial overdeepings. The strike of their alignment is offset to the northeast by 3.5 km and is sub-parallel to the mouth of the Whataroa River. We propose that these kettle holes, thought to have been carved successively during the Waimea and Otira glaciations, are the beheaded river mouth of the Whataroa river. By supposing that the furthest kettle hole was carved during the Waimea glaciation, the 3.5 km offset thus corresponds to 140 Ka of dextral slip on the Alpine fault, we could approximate the mean displacement rate over the time interval of 140-18 Ka of 25 mm/yr.</p>

Comparison of P-Wave Tomography Model in Sunda-Banda Arc by Using Data from BMKG and ISC

The tectonic setting of our study area is located between the Island of Java and Timor Leste. The complexity of this region is started with two different plates, The Indo-Australian plate and the Eurasian plate that move with different orientations and convergence rate. This area also shows active seismic activity and has a series of active volcanoes as a product of subduction and collision. To deepen understand this area, we perform delay time tomography using FMTOMO package that includes 3-D finite-difference based ray tracing and sub-space inversion procedure. We used two different sets of data, the first one is 4 years data catalog from the Indonesian Agency of Meteorology, Climatology and Geophysics, and the second one is 47 years of data from the International Seismological Centre. Data from the local Indonesian show agency shows a fewer number of events but more focus clusters. Meanwhile, the data from ISC catalog has more events and evenly distributed data. However, we also noticed that data from ISC has cluster events located at the same depth that can be improved with events relocation for better depth estimation. The Checkerboard models from both data set show a comparable result, though data from ISC show a better recovered model at a deeper depth and shallow part in the eastern area. The checkerboard from the local Agency shows slightly better results in the shallow part. Next, we invert delay time for each data set using we optimized damping and smoothing parameters. Final tomogram models show that data from the local Agency show a more continuous fast velocity band representing a downgoing subducting slab and possible back-arc thrust while results from the ISC data show a more detached fast velocity band that could be contributed from fixed depth problem in the data set. However, we noticed that data from ISC show a higher amplitude low-velocity anomaly especially in the shallow depth

Dynamic Rupture Study of Near-Field Velocity Pulses during the 2016 Kumamoto Earthquake, Japan

ABSTRACT Simulating the ground motions of future earthquakes requires a proper understanding and modeling of source, path, and site effects. Ground motions recorded during recent earthquakes very close to their ruptured faults provide new evidence of the importance of source effects and suggest that physics-based rupture modeling is critical to account for them. Here, we develop dynamic rupture models to simulate the near-fault ground motions generated by the 2016 Kumamoto, Japan, earthquake (Mw 7.0) at Nishihara village, which feature a large-amplitude velocity pulse. Comparison of mainshock and foreshock waveforms suggests that the source of the velocity pulse is on the Futagawa fault segment located very close to the site. Our dynamic models use the spectral element method and are built upon a previous kinematic description of the event via a so-called “characterized source model,” with three strong-motion generation areas (SMGAs) on the assumed fault plane. We first develop a reference model that reproduces the main features of the rupture process in agreement with previous results of kinematic source inversion. We then examine the sensitivity of the simulated near-fault ground motions to the frictional parameters (critical slip-weakening distance and stress drop) in the shallow part of the fault and to the geometrical properties of the shallow SMGA. Even assuming drastically different frictional properties in the shallow part of the fault, the amplitude of the simulated ground motions was affected little. On the other hand, changes of geometrical properties of the shallow SMGA generated large differences in simulated ground motions. The results indicate that geometrical features of the shallow SMGA played a more important role in generating near-fault ground motions with velocity pulses as observed at Nishihara village during the 2016 Kumamoto earthquake.

Millennial-scale change on a Caribbean reef system that experiences hypoxia

Coastal hypoxia has become an increasingly acknowledged threat to coral reefs that is potentially intensifying because of increased input of anthropogenic nutrients. Almirante Bay (Caribbean Panama) is a semi-enclosed system that experiences hypoxia in deeper waters which occasionally expand into shallow coral reefs, suffocating most aerobic benthic life. To explore the long-term history of reefs in the bay we extracted reef matrix cores from two reefs that today experience contrasting patterns of oxygenation. We constructed a 1800-year-long record of gastropod assemblages and isotope compositions from six U-Th chronologically-constrained reef matrix cores. We extracted two cores from each reef at 3 m water depth and two additional cores from a deeper part (4.8 m) of the hypoxia-exposed reef. Results show that the deeper part of the hypoxic reef slowed in growth and stopped accreting approximately 1500 years BP while the shallow part of the reef continued to accrete to the present day, in agreement with a model of expanding hypoxia at this time. Our proxy-based approach suggests that differences among these palaeoindicators in the two reefs may have been driven by an increase in hypoxia via eutrophication caused by either natural changes or human impacts. Similar patterns of increasing herbivores and decreasing carbon isotope values occurred in the shallow part of the hypoxic reef during the last few decades. This suggests that hypoxia may be expanding to depths as shallow as 3 m and that shallow reefs are experiencing greater risk due to increased human activity.

Investigating a tsunamigenic megathrust earthquake in the Japan Trench

The 2011 Tohoku-oki earthquake occurred in the Japan Trench 10 years ago, where devastating earthquakes and tsunamis have repeatedly resulted from subduction of the Pacific plate. Densely instrumented seismic, geodetic, and tsunami observation networks precisely recorded the event, including seafloor observations. A large coseismic fault slip that unexpectedly extended to a shallow part of megathrust fault was documented. Strong lateral variations of the coseismic slip near the trench were recorded from marine geophysical studies, along with a possible cause of these variations. The seismic activities in east Japan are still higher than those before the earthquake, and crustal deformation is still occurring. Although the recurrence probability of a great earthquake (magnitude = ~9) in the Japan Trench in the near future is very low, a large normal fault earthquake seaward of the Japan Trench is a concerning possibility.

If Not Brittle: Ductile, Plastic, or Viscous?

Integrating earthquake studies with geodynamics requires knowledge of different modes of permanent deformation of rocks beyond seismic failure. However, upon stepping out of the realm of brittle failure, students find themselves in a zone of terminology conflict. Rocks below the brittle shallow part of the lithosphere are said to be ductile, plastic, or viscous, yet in many papers what is obviously brittle deformation is said to be plastic. In this EduQuakes article, I explain the origin of this conflict and how to handle it. The primary reason for the conflict is that the word plastic is used by one research community to describe viscous deformation but by another community to describe permanent deformation that is not viscous. To the former community, emphasis is on microscopic deformation mechanisms. To the latter community, emphasis is on whether the macroscopic deformation is time dependent. Using a Coulomb continuum to approximate the effects of numerous brittle faults adds another level of complexity. It is futile to expect a unification of terminology any time soon, but with some basic knowledge one can live with this situation without suffering scientific confusion.

ASSIMILATION CAPACITY OF THE MARGINAL FILTER OF THE ECOSYSTEM OF THE ESTUARINE COAST OF THE VOLGA

According to the data of long-term observations, the assessment of the degree of impact of copper and zinc on the ecosystem of the shallow part of the estuarine coast of the Volga River was carried out. There are the ideas of the marginal filter and the assimilation capacity were used in the article. The calculation of the assimilation capacity for a marginal filter significantly based on the dimensional characteristics, such as the estuarine region of the Volga River, was carried out at several points located within the estuarine seashore. In this work the century-old sections of the state observation network were used. It can be seen from the calculated data that the value of the assimilation capacity is subject to significant intra-and inter-annual fluctuations. The main parameter determining the volume of the assimilation capacity of copper and zinc is fairly called the flow of the Volga River. According to the results of the study, it can be argued that the observed level of copper and zinc runoff into the Caspian Sea is completely assimilated in the shallow part of the seashore.