Climate variability and predictability associated with the Indo-Pacific Oceanic Channel Dynamics in the CCSM4 Coupled System Model

An experiment using the Community Climate System Model (CCSM4), a participant of the Coupled Model Intercomparison Project phase-5 (CMIP5), is analyzed to assess the skills of this model in simulating and predicting the climate variabilities associated with the oceanic channel dynamics across the Indo-Pacific Oceans. The results of these analyses suggest that the model is able to reproduce the observed lag correlation between the oceanic anomalies in the southeastern tropical Indian Ocean and those in the cold tongue in the eastern equatorial Pacific Ocean at a time lag of 1 year. This success may be largely attributed to the successful simulation of the interannual variations of the Indonesian Throughflow, which carries the anomalies of the Indian Ocean Dipole (IOD) into the western equatorial Pacific Ocean to produce subsurface temperature anomalies, which in turn propagate to the eastern equatorial Pacific to generate ENSO. This connection is termed the “oceanic channel dynamics” and is shown to be consistent with the observational analyses. However, the model simulates a weaker connection between the IOD and the interannual variability of the Indonesian Throughflow transport than found in the observations. In addition, the model overestimates the westerly wind anomalies in the western-central equatorial Pacific in the year following the IOD, which forces unrealistic upwelling Rossby waves in the western equatorial Pacific and downwelling Kelvin waves in the east. This assessment suggests that the CCSM4 coupled climate system has underestimated the oceanic channel dynamics and overestimated the atmospheric bridge processes.     

Succession and seasonal variation in epilithic biofilms on artificial reefs in culture waters of the sea cucumber <Emphasis Type="Italic">Apostichopus japonicus</Emphasis>

Periphytic biofilms in aquaculture waters are thought to improve water quality, provide an additional food source, and improve the survival and growth of some reared animals. In the Asia- Pacific region, particularly in China, artificial reefs are commonly used in the commercial farming of sea cucumbers. However, few studies have examined the epilithic biofilms on the artificial reefs. To gain a better understanding of the succession of epilithic biofilms and their ecological processes in sea cucumber culture waters, two experiments were conducted in culture waters of the sea cucumber Apostichopus japonicus in Rongcheng, China, using artificial test panels. On the test panels of succession experiment, more than 67 species were identified in the biofilms. On the test panels of seasonal variation experiment, more than 46 species were recorded in the biofilms. In both experiments, communities of epilithic biofilms were dominated by diatoms, green algae and the annelid Spirorbis sp. In the initial colonization, the dominant diatoms were Cocconeis sp., Amphora spp. and Nitzschia closterium in June, which were succeeded by species of Navicula, Cocconeis and Nitzschia (July to September), and then by Licmophora abbreviata, Nitzschia closterium and Synedra spp. in the following months. A diatom bloom in the autumn and filamentous green algae burst in the summer were also observed. Ecological indices well annotated the succession and seasonal changes in epilithic communities. Multidimensional scaling (MDS) analysis found significant differences in diatom community composition among months and seasons. Fast growth of biofilms was observed in the summer and autumn, whereas the biomass of summer biofilms was largely made up of filamentous green algae. Present results show that the components of epilithic biofilms are mostly optimal foods of A. japonicus, suggesting that biofilms on artificial reefs may contribute important nutritional sources for sea cucumbers during their growth seasons. Future works should include quantitative determination of the contribution of epilithic biofilms to the diet of A. japonicus, potential roles of epilithic biofilms in regulating the water quality of sea cucumber ponds, and the regulation of epilithic biofilms in sea cucumber culture ponds.     

Enhanced Oxygen Isotope Determination in Uranium Oxides Using BrF5 Fluorination

A new method for accurate determination of oxygen isotopes in uranium oxides encountered in the nuclear fuel cycle was developed using the conventional BrF₅ fluorination technique. Laser‐assisted fluorination was tested for comparison. We focused on fine powders of triuranium octoxide (U₃O₈), uranium dioxide (UO_2±x with 0 ≤ x ≤ 0.25), uranium trioxide (UO₃.nH₂O, with 0.8 ≤ n ≤ 2) and diuranates (M₂U₂O₇.nH₂O, with M = NH₄, Na or Mg_0.5 and 0 ≤ n ≤ 6). Fluorination at room temperature and heating under vacuum at 150 °C are shown to eliminate both adsorbed and structural water from the powder samples. Precision fit for purpose of δ¹⁸O values (± 0.3‰, 1s) and oxygen yields (close to 100%) were obtained for U₃O₈ and UO₂ where oxygen is only bound to uranium. A lower precision was observed for UO₃.nH₂O and M₂U₂O₇.nH₂O where oxygen is both present in the structural H₂O and bonded to uranium and where the extracted O_2(g) can be contaminated by NF₃ and NO_x compounds. Laser‐assisted fluorination gave shifted δ¹⁸O values between +0.8 and +1.4‰ for U₃O₈, around ?0.8‰ for UO₃.nH₂O and between ?3.9 and ?4.5‰ for M₂U₂O₇.nH₂O (± 0.3‰, 1s) compared with the conventional method.     

A Workflow for Static Reservoir Modeling Guided by Seismic Data in a Fluvial System

Realistic and accurate static geologic models are an essential element needed to predict the behavior of subsurface reservoirs and play an important role in petroleum engineering. Data used in the development of a static geologic model are gathered from various sources, such as seismic, log, and core data, each of them providing information on different physical properties of interest and with varying degrees of resolution. Compiling all data from various sources into a single representation of the subsurface formation of interest is a daily challenge for many petroleum geologists and engineers. This paper describes a framework to develop and select process-mimicking models that are consistent with available seismic attributes, namely impedance. Using a process-mimicking modeling package, 75 models of a fluvial meandering system are generated, one of which is chosen as the “true” model and masked thereafter. The implemented selection method relies on the degree of similarity in the histogram of representations of clusters of all possible patterns in the seismic impedance domain based on each process-mimicking model and that of the “true” model at several resolutions. The results demonstrate the effectiveness of the use of a weighted average divergence distance across multiple levels to select process-mimicking models that honor seismic data the best.     

Crustal structure of the Southwest Subbasin,South China Sea,from wide-angle seismic tomography and seismic reflection imaging

The Southwest Subbasin (SWSB) is an abyssal subbasin in the South China Sea (SCS), with many debates on its neotectonic process and crustal structure. Using two-dimensional seismic tomography in the SWSB, we derived a detailed P-wave velocity model of the basin area and the northern margin. The entire profile is approximately 311-km-long and consists of twelve oceanic bottom seismometers (OBSs). The average thickness of the crust beneath the basin is 5.3 km, and the Moho interface is relatively flat (10–12 km). No high velocity bodies are observed, and only two thin high-velocity structures (~7.3 km/s) in the layer 3 are identified beneath the northern continent-ocean transition (COT) and the extinct spreading center. By analyzing the P-wave velocity model, we believe that the crust of the basin is a typical oceanic crust. Combined with the high resolution multi-channel seismic profile (MCS), we conclude that the profile shows asymmetric structural characteristics in the basin area. The continental margin also shows asymmetric crust between the north and south sides, which may be related to the large scale detachment fault that has developed in the southern margin. The magma supply decreased as the expansion of the SWSB from the east to the west.     

Temporal Variability of Total Ozone in the Asian Region Inferred from Ground-Based and Satellite Measurement Data

This paper reports investigation data on the temporal variability of total ozone content (TOC) in the Central Asian and Tibet Plateau mountain regions obtained by conventional methods, as well as by spectral, cross-wavelet, and composite analyses. The data of ground-based observation stations located at Huang He, Kunming, and Lake Issyk-Kul, along with the satellite data obtained at SBUV/SBUV2 (SBUV merged total and profile ozone data, Version 8.6) for 1980–2013 and OMI (Ozone Monitoring Instrument) and TOU (Total Ozone Unit) for 2009–2013 have been used. The average relative deviation from the SBUV/SBUV2 data is less than 1% in Kunming and Issyk-Kul for the period of 1980–2013, while the Huang He Station is characterized by an excess of the satellite data over the ground-based information at an average deviation of 2%. According to the Fourier analysis results, the distribution of amplitudes and the periods of TOC oscillations within a range of over 14 months is similar for all series analyzed. Meanwhile, according to the cross-wavelet and composite analyses results, the phase relationships between the series may considerably differ, especially in the periods of 5–7 years. The phase of quasi-decennial oscillations in the Kunming Station is close to the 11-year oscillations of the solar cycle, while in the Huang He and Issyk-Kul stations the TOC variations go ahead of the solar cycle.     

Coseismic Fault Slip of the September 16, 2015 <Emphasis Type="Italic">Mw</Emphasis> 8.3 Illapel,Chile Earthquake Estimated from InSAR Data

The complete surface deformation of 2015 Mw 8.3 Illapel, Chile earthquake is obtained using SAR interferograms obtained for descending and ascending Sentinel-1 orbits. We find that the Illapel event is predominantly thrust, as expected for an earthquake on the interface between the Nazca and South America plates, with a slight right-lateral strike slip component. The maximum thrust-slip and right-lateral strike slip reach 8.3 and 1.5 m, respectively, both located at a depth of 8 km, northwest to the epicenter. The total estimated seismic moment is 3.28 × 10²¹ N.m, corresponding to a moment magnitude Mw 8.27. In our model, the rupture breaks all the way up to the sea-floor at the trench, which is consistent with the destructive tsunami following the earthquake. We also find the slip distribution correlates closely with previous estimates of interseismic locking distribution. We argue that positive coulomb stress changes caused by the Illapel earthquake may favor earthquakes on the extensional faults in this area. Finally, based on our inferred coseismic slip model and coulomb stress calculation, we envision that the subduction interface that last slipped in the 1922 Mw 8.4 Vallenar earthquake might be near the upper end of its seismic quiescence, and the earthquake potential in this region is urgent.     

The Seismotectonics of the Po Plain (Northern Italy): Tectonic Diversity in a Blind Faulting Domain

We present a systematic and updated overview of a seismotectonic model for the Po Plain (northern Italy). This flat and apparently quiet tectonic domain is, in fact, rather active as it comprises the shortened foreland and foredeep of both the Southern Alps and the Northern Apennines. Assessing its seismic hazard is crucial due to the concentration of population, industrial activities, and critical infrastructures, but it is also complicated because (a) the region is geologically very diverse, and (b) nearly all potential seismogenic faults are buried beneath a thick blanket of Pliocene–Pleistocene sediments, and thus can be investigated only indirectly. Identifying and parameterizing the potential seismogenic faults of the Po Plain requires proper consideration of their depth, geometry, kinematics, earthquake potential and location with respect to the two confronting orogens. To this end, we subdivided them into four main, homogeneous groups. Over the past 15 years we developed new strategies for coping with this diversity, resorting to different data and modeling approaches as required by each individual fault group. The most significant faults occur beneath the thrust fronts of the Ferrara-Romagna and Emilia arcs, which correspond to the most advanced and buried portions of the Northern Apennines and were the locus of the destructive May 2012 earthquake sequence. The largest known Po Plain earthquake, however, occurred on an elusive reactivated fault cutting the Alpine foreland south of Verona. Significant earthquakes are expected to be generated also by a set of transverse structures segmenting the thrust system, and by the deeper ramps of the Apennines thrusts. The new dataset is intended to be included in the next version of the Database of Individual Seismogenic Sources (DISS; http://diss.rm.ingv.it/diss/, version 3.2.0, developed and maintained by INGV) to improve completeness of potential sources for seismic hazard assessment.     

Large Earthquakes at the Ibero-Maghrebian Region: Basis for an EEWS

Large earthquakes (M_w > 6, I_max > VIII) occur at the Ibero-Maghrebian region, extending from a point (12ºW) southwest of Cape St. Vincent to Tunisia, with different characteristics depending on their location, which cause considerable damage and casualties. Seismic activity at this region is associated with the boundary between the lithospheric plates of Eurasia and Africa, which extends from the Azores Islands to Tunisia. The boundary at Cape St. Vincent, which has a clear oceanic nature in the westernmost part, experiences a transition from an oceanic to a continental boundary, with the interaction of the southern border of the Iberian Peninsula, the northern border of Africa, and the Alboran basin between them, corresponding to a wide area of deformation. Further to the east, the plate boundary recovers its oceanic nature following the northern coast of Algeria and Tunisia. The region has been divided into four zones with different seismic characteristics. From west to east, large earthquake occurrence, focal depth, total seismic moment tensor, and average seismic slip velocities for each zone along the region show the differences in seismic release of deformation. This must be taken into account in developing an EEWS for the region.     

Interpretation of magnetic and gravity gradient tensor data using normalized source strength – A case study from McFaulds Lake,Northern Ontario,Canada

In this paper, we present a case study on the use of the normalized source strength (NSS) for interpretation of magnetic and gravity gradient tensors data. This application arises in exploration of nickel, copper and platinum group element (Ni‐Cu‐PGE) deposits in the McFaulds Lake area, Northern Ontario, Canada. In this study, we have used the normalized source strength function derived from recent high resolution aeromagnetic and gravity gradiometry data for locating geological bodies. In our algorithm, we use maxima of the normalized source strength for estimating the horizontal location of the causative body. Then we estimate depth to the source and structural index at that point using the ratio between the normalized source strength and its vertical derivative calculated at two levels; the measurement level and a height h above the measurement level. To discriminate more reliable solutions from spurious ones, we reject solutions with unreasonable estimated structural indices. This method uses an upward continuation filter which reduces the effect of high frequency noise. In the magnetic case, the advantage is that, in general, the normalized magnetic source strength is relatively insensitive to magnetization direction, thus it provides more reliable information than standard techniques when geologic bodies carry remanent magnetization. For dipping gravity sources, the calculated normalized source strength yields a reliable estimate of the source location by peaking right above the top surface. Application of the method on aeromagnetic and gravity gradient tensor data sets from McFaulds Lake area indicates that most of the gravity and magnetic sources are located just beneath a 20 m thick (on average) overburden and delineated magnetic and gravity sources which can be probably approximated by geological contacts and thin dikes, come up to the overburden.