Nonvolcanic tremor observed in the Mexican subduction zone

Nonvolcanic tremor (NVT) activity is revealed as episodes of higher spectral amplitude at 1–8 Hz in daily spectrograms from the continuous seismological records in Guerrero, Mexico. The analyzed data cover a period of 2001–2007 when in 2001–2002 a large slow slip event (SSE) had occurred in the Guerrero-Oaxaca region, and then a new large SSE occurred in 2006. The tremor burst is dominated by S-waves. More than 100 strong NVT bursts were recorded in the narrow band of ~40 × 150 km^2 to the south of Iguala City and parallel to the coastline. Depths of NVT hypocenters are mostly scattered in the continental crust between 5 and 40 km depth. Tremor activity is higher during the 2001–2002 and 2006 SSE compared with that for the “quiet” period of 2003–2005. While resistivity pattern in Guerrero does not correlate directly with the NVT distribution, gravity and magnetic anomaly modeling favors a hypothesis that the NVT is apparently related to the dehydration and serpentinization processes

Principles and methods of efficient organization of vertically integrated structures in the agro-industrial sector

The article considers the principles and τηε organizational methods of vertically integrated structures, in particular vertical integration in the agro-industrial sector. It analyzes the peculiarities of development of the Black sea-Caspian region. The peculiarities of functioning in agro-industrial enterprises are revealed and the problem of using logistic tools in domestic business it is formulated. The article is devoted to solve actual scientific and practical tasks to ensure the efficient production and the sale of products with the lowest cost, providing freedom in the development of strategies for competitiveness, effective economic, financial, and personnel policy. The result of the research is to develop proposals on formation of logistic chains in the agro-industrial sector by considering the market, the economic policy of the regional authorities, the regulatory and legal acts constituting the legal basis of the organization of agro-industrial sector as given conditions. The article provides recommendations on the organization of vertically integrated structures in the agro-industrial sector with the purpose to increase management efficiency for the agricultural enterprises.peer-reviewe

Tools to improve the efficiency of import substitution in the agro-industrial complex under economic sanctions

Purpose: This article is concentrated on the creation of a uniform risk management system in agro-industrial complex which can increase efficiency of control over compliance with non-tariff restrictions and will strengthen protection of agricultural producers against importing sanctions. Structure/Methodology/Approach: If it is necessary to evaluate the prospects of increasing efficiency of import substitution in agro-industrial complex in the conditions of sanctions first, you need to allocate types of import dependence of various branches. Second, you need to analyze the main instruments of implementation of import substitution policy. Third, you need to create a uniform risk management system in the Eurasian customs' territory for increasing efficiency of import substitution. Findings: The authors offer creation of a uniform risk management system which application will increase efficiency of control over compliance with non-tariff restrictions. Practical Implamentation: Results can be implemented in administrative practice for the purpose of increasing efficiency of import substitution in the agro- industrial complex. Originality/value: The main contribution of this research consists in development of the system of increasing effective risk management in member states of EEU.peer-reviewe

Relating the long-term and short-term vertical deformation across a transect of the forearc in the central Mexican subduction zone

Earthquake-cycle deformation, which includes earthquake ruptures, interseismic strain, and transient slow slip events, spans spatial scales ranging from fractions of a meter to thousands of kilometers. Similarly, temporal scales range from seconds during an earthquake rupture to thousands of years of strain accumulation between earthquakes. We discuss results regarding the vertical crustal deformation associated with both slow and rapid crustal deformation across a transect of the central Mexican subduction forearc in the Guerrero seismic gap, where the Cocos plate underthrusts the North America plate. This sector of the subduction zone is characterized by a flat-slab geometry with zones of sharp bending-unbending of the slab, irregularly distributed seismicity, and exceptionally large slow slip events. We used the river network, topography, geomorphic features, and morphometry on a transect across the forearc to assess Quaternary crustal deformation. The Papagayo drainage network shows that the forearc has been uplifted since the late Cenozoic (~25 Ma), and that rates of uplift increased since the beginning of the Holocene. Uplift is not homogeneous but shows a trend of increase away from the coast. This vertical deformation is strongly influenced by subduction processes. Thus, the Papagayo River network is strongly controlled by Holocene earthquake cycle processes. This is particularly true for the southern section of the drainage basin, where E-W-striking left-lateral strike-slip faults with a vertical component offset the course of the main river. These faults are accommodating part of the oblique plate convergence at the Mexican subduction zone. We measured the height of a series of terraces and dated quartz extracts by optically stimulated luminescence, and we calculated long-term rates of uplift ranging from 0.5 to 4.9 mm/yr. We discuss associations of forearc topography, faults, and long-term crustal deformation with the Cocos slab geometry, distribution of slow slip events, and earthquake-cycle deformation

Temporal variations of non-volcanic tremor (NVT) locations in the Mexican subduction zone: Finding the NVT sweet spot.

International audienceEpicentral locations of non-volcanic tremors (NVT) in the Mexican subduction zone are determined from the peak of the energy spatial distribution and examined over time. NVT is found to occur persistently at a distance of ∼215 km from the trench, which we term the "Sweet Spot" because this region probably has the proper conditions (i.e., temperature, pressure, and fluid content) for the NVT to occur with minimum shear slip. High-energy NVT episodes are also observed every few months, extending ∼190 km to ∼220 km from the trench with durations of a few weeks. During the 2006 slow slip event (SSE) the duration and the recurrence rate of the NVT episodes increased. Low-energy episodes were also observed, independent from the high-energy episodes, ∼150 km to ∼190 km from the trench during the 2006 SSE. Both the high and low energy episodes were made up of many individual NVT's that had a range of energy-release-rates. However, the highest energy-release-rates of the high-energy episodes were consistently double those of the low-energy episodes and the persistent activity at the Sweet Spot. We suggest that all of the high-energy episodes are evidence of small, short repeat interval SSE. Given this model, the increased recurrence rate of the high-energy NVT episodes during the 2006 long-term SSE implies that short-term SSE's also increase during the SSE and are therefore triggered by the SSE

Active 650-km Long Fault System and Xolapa Sliver in Southern Mexico

New estimates of long-term velocities of permanent GPS stations in Southern Mexico reveal that the geologically discernible 650-km long shear zone, which strikes parallel to the Middle America trench, is active. This left-lateral strike-slip, La Venta–Chacalapa (LVC) fault system, is apparently associated with a motion of the Xolapa terrain and at the present time is the northern boundary of a 110–160-km wide forearc sliver with a sinistral motion of 3–6 mm/year with respect to the North America plate. This sliver is the major tectonic feature in the Guerrero and Oaxaca regions, which accommodates most of the oblique component of the convergence between the Cocos and North America plates. Previous studies based purely on the moment tensor coseismic slips exceedingly overestimated the sliver inland extent and allocated its northern margin on or to the north of the Trans-Mexican Volcanic Belt. While the LVC fault system probably slips slowly over geologic scale time and there is not any historic evidence of large earthquakes on the fault so far, its seismic potential could be very high, assuming a feasible order of 103 years recurrence cycle. A detailed analysis of long-term position time series of permanent GPS stations in the Guerrero and Oaxaca states, Southern Mexico discards previous models and provides clear evidence of an active LVC fault zone bounding the Xolapa forearc sliver. The southeastward motion of this sliver may have persisted for the last 8–10 Million year and played an important role in the tectonic evolution of the region

GPS Constraints on the Mw = 7.5 Ometepec Earthquake Sequence, Southern Mexico: Coseismic and Post-Seismic Deformation

We use continuous GPS measurements from 31 stations in southernMexico to model coseismic slip and post-seismic deformation from the 2012 March 20 Mw = 7.5 Ometepec earthquake, the first large thrust earthquake to occur below central Mexico during the modern GPS era. Coseismic offsets ranging from ∼280 mm near the epicentre to 5 mm or less at sites far from the epicentre are fit best by a rupture focused between ∼15 and 35 km depth, consistent with an independent seismological estimate. The corresponding geodetic moment of 1.4 × 1020 N·m is within 10 per cent of two independent seismic estimates. Transient post-seismic motion recorded by GPS sites as far as 300 km from the rupture has a different horizontal deformation gradient and opposite sense of vertical motion than do the coseismic offsets. A forward model of viscoelastic relaxation as a result of our new coseismic slip solution incorrectly predicts uplift in areas where post-seismic subsidence was recorded and indicates that viscoelastic deformation was no more than a few per cent of the measured post-seismic deformation. The deformation within 6 months of the earthquake was thus strongly dominated by fault afterslip. The post-seismic GPS time-series are well fit as logarithmically decaying fault afterslip on an area of the subduction interface up to 10 times larger than the earthquake rupture zone, extending as far as 220 km inland. Afterslip had a cumulative geodetic moment of 2.0 × 1020 N·m, ∼40 per cent larger than the Ometepec earthquake. Tests for the shallow and deep limits for the afterslip require that it included much of the earthquake rupture zone as well as regions of the subduction interface where slow slip events and non-volcanic tremor have been recorded and areas even farther downdip on the flat interface. Widespread afterslip below much of central Mexico suggests that most of the nearly flat subduction interface in this region is conditionally stable and thus contributes measurable transient deformation to large areas of Mexico south of and in the volcanic belt