Basic Relations for Studying the Influence of Geophysical Processes on the Earth’s Rotation: The Angular Momentum Approach

Relations to study the influence of geophysical processes on the temporally varying rotation of the Earth are considered. Liouville’s equations of rotational motion are derived for a two-component Earth model (consisting of a solid mantle and a fluid core) and suitably simplified for calculations of the influence of mass redistributions on the Earth’s rotational behaviour. Excitation functions, or effective angular momentum functions, describing the influence of mass redistributions on the equations of rotational motion are derived, and their calculation is elucidated by some examples. Relations between temporally varying second degree Stokes coefficients of the gravity field and excitation functions are discussed. Different solutions of the equations of rotational motion are described. The identification of exciting geophysical processes by the kinematics of the inverse calculated excitation function is portrayed.     

The Relationship Between the Interannual Variation of Earth’s Rotation and El Niño Events

We analyzed the relationship between the earth’s rotational variation and sea-surface temperature anomaly. By means of using Fast Fourier Transform (FFT) bandpass filter on the change of length-of-day (ΔLOD) data, the interannual variation series having time periods greater than 1.5-year and less than 8-year was obtained. Time series analyses of the interannual variation, which corresponds to the El Niño period, reveal a close linkage between the earth’s rotation and El Niño. A detailed comparison suggests, that six of seven El Niño events are nearly synchronous with the interannual variation of the earth’s rotation, and all ΔLOD peak are in El Niño years except 1991–92, which means the interannual variation of the earth’s rotation in these years is relatively slow. The correlation between ΔLOD and sea-surface temperature is about 0.517 (1 month-lag), which far exceeds the 99% significance level.     

The Effects of Solar Eclipse of August 1, 2008 on Earth’s Atmospheric Parameters

Several experiments were undertaken at Kolkata (latitude: 22°34′N, longitude: 88°30′E) on the solar eclipse day of August 1, 2008 to observe the effects of the solar eclipse on Fair Weather Field (FWF) and VLF amplitude and phase. The experimental results presented here show significant deviations of the observed parameters from their normal values, as they are determined by the average of the records obtained on 5 days adjacent to the day of the solar eclipse.     

The Relationship between Multifractal and Entropy Properties of Seismic Noise in Kamchatka and Irregularity of the Earth’s Rotation

Izvestiya, Physics of the Solid Earth - Abstract—The connection between the properties of seismic noise continuously recorded by the network of 21 broadband seismic stations in...     

The Influence of Earth Temperature on the Dynamic Characteristics of Frozen Soil and the Parameters of Ground Motion on Sites of Permafrost

Earth temperature is one of the most important factors influencing the mechanical properties of frozen soil. Based on the field investigation of the characteristics of ground deformation and ground failure caused by the Ms8.1 earthquake in the west of the Kuniun Mountain Pass,China, the influence of temperature on the dynamic constitutive relationship, dynamic elastic modulus, damping ratio and dynamic strength of frozen soil was quantitatively studied by means of the dynamic triaxial test. Moreover, the characteristics of ground motion on a permafrost site under different temperatures were analyzed for the four profiles of permafrost along the Qinghai-Xizang (Tibet) Railway using the time histories of ground motionacceleration with 3 exceedance probabilities of the Kunlun Mountains area. The influences of temperature on the seismic displacement, velocity, acceleration and response spectrum on permafrost ground were studied quantitatively. A scientific basis was presented for earthquake disaster mitigation for engineering foundations, highways and underground engineering in permafrost areas.     

Space–Time Earthquake Prediction: The Error Diagrams

The quality of earthquake prediction is usually characterized by a two-dimensional diagram n versus τ, where n is the rate of failures-to-predict and τ is a characteristic of space–time alarm. Unlike the time prediction case, the quantity τ is not defined uniquely. We start from the case in which τ is a vector with components related to the local alarm times and find a simple structure of the space–time diagram in terms of local time diagrams. This key result is used to analyze the usual 2-d error sets {n, τ _w } in which τ _w is a weighted mean of the τ components and w is the weight vector. We suggest a simple algorithm to find the (n, τ _w ) representation of all random guess strategies, the set D, and prove that there exists the unique case of w when D degenerates to the diagonal n + τ _w  = 1. We find also a confidence zone of D on the (n, τ _w ) plane when the local target rates are known roughly. These facts are important for correct interpretation of (n, τ _w ) diagrams when we discuss the prediction capability of the data or prediction methods.     

Laboratory Modeling of Aftershock Sequences: Stress Dependences of the Omori and Gutenberg–Richter Parameters

Izvestiya, Physics of the Solid Earth - Laboratory experiments on studying the aftershock regime are carried out on sandstone specimens at different levels of axial loading and uniform compression...     

The Grad-Shafranov reconstruction in twenty years: 1996–2016

We review and summarize the applications of the Grad-Shafranov (GS) reconstruction technique to space plasma structures in the Earth’s magnetosphere and in the interplanetary space. We organize our presentations following the branches of the “academic family tree” rooted on Prof. Bengt U. Ö. Sonnerup, the inventor of the GS method. Special attentions are paid to validations of the GS reconstruction results via (1) the direct validation by co-spatial in-situ measurements among multiple spacecraft, and (2) indirect validation by implications and interpretations of the physical connection between the structures reconstructed and other related processes. For the latter, the inter-comparison and interconnection between the large-scale magnetic flux ropes (i.e., Magnetic Clouds) in the solar wind and their solar source properties are presented. In addition, we also summarize various GS-type (or -like) reconstruction and an extension of the GS technique to toroidal geometry. In particular, we point to a possible advancement with added complexity of “helical symmetry” and mixed helicity, in the hope of stimulating interest in future development. We close by offering some thoughts on appreciating the scientific merit of GS reconstruction in general.     

The seismicity of the Kamchatka region: 1962–2011

This paper reviews the Kamchatka seismicity for a 50-year period of observation. These data were used to carry out a regionalization of Kamchatka’s seismic volume and adjacent areas. In all, ten zones were identified with differing activities and origins of seismicity. A comparative analysis was carried out for the seismicity in the more active zones. We found significant differences between the structures of the southern and the northern segment in the Kamchatka part of the Kuril-Kamchatka subduction zone. Seismological data corroborated a relationship between the subduction zone and the underthrusting of the Pacific plate under the Eurasian plate. These data from the 50-year period of observation helped identify a new Koryak seismic belt that encompasses the northwestern coast of the Bering Sea. We provide a brief review of macroseismic effects due to the most significant earthquakes for the 1962–2010 period.     

The Luingo caldera: The south-easternmost collapse caldera in the Altiplano–Puna plateau,NW Argentina

This article identifies the Pucarilla–Cerro Tipillas Volcanic Complex and its major eruptive source, the Luingo caldera (26° 10′S–66° 40′W). Detailed geological mapping, stratigraphic sections, facies analysis and correlations, including the identification of typical caldera components, allow us to infer the position of a collapse caldera, elongated at N65° and with a diameter of 19 km × 13 km, which is responsible for an eruption of 135 km³ (DRE) of magma. The high-crystal contents of the associated ignimbrites, combined with its tectonic setting, indicate that regional and local tectonic structures played a crucial role in the formation of the caldera.     

Early-stage rifting of the Southern Tyrrhenian region: The Calabria–Sardinia breakup

The Southern Tyrrhenian Sea is an extensional basins linked to the Neogene evolution of the Calabria subduction zone located in the western Mediterranean realm where controversial kinematic and geodynamical models have been proposed. Our study provides a key to unravel timing and mode of extension of the upper plate and the breakup of Calabria from Sardinia. By combining original stratigraphic analysis of wells and seismic profiles off Calabria with a stratigraphic correlation to onshore outcrops, we re-assess the tectonic evolution that controlled the sedimentation and basement deformation of the Southern Tyrrhenian basin during Serravallian–Tortonian times. We document the tectono-stratigraphic evolution of adjacent extensional basins characterized by 3rd order depositional sequences (Ser1, Tor1 and Tor2) and different modes of extension, subsidence and opposite dipping faults. Episodic basin development is recorded by a coarsening-up and fining-up trend of the sedimentary succession and by tectonically enhanced unconformities that reflect three episodes of fault activity. We reconstruct Serravallian–Tortonian paleogeographic maps and propose a block faulting model for the evolution of the Sardinia–Calabria area. Sardinia was disconnected from Calabria through N–S normal faults forming Tyrrhenian extensional basins that formed contemporaneously to the E–W opening of the Algerian basin. Unlike published Serravallian–Tortonian reconstructions of the western Mediterranean realm, our results support a geodynamic model characterized by rapid trench retreat, trench-normal extension in the entire overriding plate and very weak coupling between plates.     

Sun–Earth geometry,geomagnetic activity,and planetary F2 layer ion density: Part I: Signatures of magnetic reconnection

Our previous quantitative analyses have shown that geomagnetic activity and planetary ion density of the F2 layer of the ionosphere seem to share the same parent cause, the solar wind, whose entry into geospace is controlled by the Sun–Earth geometry. The thrust of this paper is four fold: (a) to establish the reality of this not clearly recognized connection, (b) to demonstrate that geomagnetic activity varies seasonally with three separate and independent components, viz. a semiannual, an annual and a Sun–Earth-distance determined component, all of which can be accurately derived from solar–terrestrial geometry alone, (c) to evaluate the contribution of each of these components which, taken together, appear to represent the steady-state signatures of the mechanism of magnetopause reconnection, and (d) to highlight the fact that the currently used planetary geomagnetic indices are deficient and therefore need to be revised. Since detailed understanding of the precise mechanism of the entry of solar wind energy into geospace is still lacking, no mechanism is suggested to show how solar wind energy is transported to the F2 layer (including low and equatorial latitudes). Magnetospheric electric fields, precipitation of energetic neutrals produced through charge exchange reactions with ions in the ring current and radiation belt particles, Joule heating, etc., may all be involved, but the energy for all such processes still comes from the solar wind. Apart from the three components of the reconnection mechanism mentioned above, a steady component due to the viscous interaction mechanism should also be present.     

The geoecological impact of eruptions on Karymskii Volcano and Tokareva crater, Eastern Kamchatka: The 1996–2008 observations

This paper considers the geoecological impacts of eruptions on Karymskii Volcano and the Tokareva crater for the 1996–2008 period, which resulted in changes in (a) the relief around these edifices, (b) the discharge and composition of water in the Karymskii River and other streams in the area, and (c) the discharge and composition of gases in thermal springs. It was found that the concentration of CH₄ previously had been abnormally high in free gases that emanate from the new Piipovskii Springs and an explanation is provided of the decrease in their concentration over time. We detected variations in the radon activity, OARn (Bq/m³), in free gases that are released in the Karymskii caldera hydrothermal occurrences; the variations are consistent with those in the eruptive activity of Karymskii Volcano in 2005–2006. We describe permafrost rocks in the Karymskii caldera that favor the generation of a cryolithic zone.     

The K Method for Estimating Earthquake Activity Parameters and Effect of the Boundary Uncertainty of the Source Region:Discussion on the Seismic Zoning Method

Two aspects of a new method,which can be used for seismic zoning,are introduced in this paper.On the one hand,the approach to estimate b value and annual activity rate proposed by Kijko and Sellevoll needs to use the earthquake catalogue.The existing earthquake catalogue contains both historical and recent instrumental data sets and it is inadequate to use only one part.Combining the large number of historical events with recent complete records and taking the magnitude uncertainty into account,Kijko's method gives the maximum likelihood estimation of b value and annual activity rate,which might be more realistic.On the other hand,this method considers the source zone boundary uncertainty in seismic hazard analysis,which means the earthquake activity rate across a boundary of a source zone changes smoothly instead of abruptly and avoids too large a gradient in the calculated results.     

Earth-Affecting Solar Causes Observatory (EASCO): A potential International Living with a Star Mission from Sun–Earth L5

This paper describes the scientific rationale for an L5 mission and a partial list of key scientific instruments the mission should carry. The L5 vantage point provides an unprecedented view of the solar disturbances and their solar sources that can greatly advance the science behind space weather. A coronagraph and a heliospheric imager at L5 will be able to view CMEs broadsided, so space speed of the Earth-directed CMEs can be measured accurately and their radial structure discerned. In addition, an inner coronal imager and a magnetograph from L5 can give advance information on active regions and coronal holes that will soon rotate on to the solar disk. Radio remote sensing at low frequencies can provide information on shock-driving CMEs, the most dangerous of all CMEs. Coordinated helioseismic measurements from the Sun–Earth line and L5 provide information on the physical conditions at the base of the convection zone, where solar magnetism originates. Finally, in situ measurements at L5 can provide information on the large-scale solar wind structures (corotating interaction regions (CIRs)) heading towards Earth that potentially result in adverse space weather.     

The unusual 2014–2016 El Ni?o events: Dynamics,prediction and enlightenments

The 2014–2016 El Ni?o events consist of a stalled El Ni?o event in the winter of 2014/2015 and a following extreme El Ni?o event in the end of 2015. Neither event was successfully predicted in operational prediction models. Because of the unusual evolutions of these events that rarely happened in the historical observations, few experience was ready for understanding and predicting the two El Ni?o events when they occurred. Also due to their specialties, considerable attention were attracted with aims to reveal the hidden mechanisms. This article reviews the recent progresses and knowledge that were obtained in these studies. Emerging from these studies, it was argued that the key factor that was responsible for the stalled El Ni?o in 2014 was the unexpected summertime Easterly Wind Surges(EWSs) or the lack of summertime Westerly Wind Bursts(WWBs). Most operational prediction models failed to reproduce such stochastic winds and thus made unrealistic forecasts. The two El Ni?o events awakened the research community again to incorporate the state-of-the-art climate models to simulate the stochastic winds and investigate their roles in the development of El Ni?o.