SEISMICITY of CENTRAL ASIA in 2015 (Kyrgyzstan, Uzbekistan and Southeastern Kazakhstan)

Seismic observations on the territory of Central Asia in 2015 were carried out by monitoring systems of three countries: Kyrgyzstan, Uzbekistan and Kazakhstan consisting of 25, 29 stations of the first two countries and 43 stations and five seismic groups of the third country respectively. The catalogue of earthquakes in 2015 included 302 events with KR=8.614.1. The largest earthquake in the catalogue with KR=14.1 was registered on November 17, 2015, at 17h 29m in the Osh area of Kyrgyzstan, near the Taldyk settlement. It was accompanied by numerous aftershocks (852) with KR=4.111.4. In general, the seismic situation in the region in 2015 is characterized by lower values of the number of earthquakes N and the released seismic energy E compared to the average annual values of these parameters for the period from 1996 to 2014. The location and configuration of the main seismically active zones remained without changes.

SEISMICITY of the CARPATHIANS in 2015

The article describes seismic observations in the Carpathian region in 2015, which were carried out, as before, by two organizations from two states: in Ukraine – the Seismicity department of the Carpathian region of the Institute of Geophysics of the NAS of Ukraine, in Moldova – the Seismology laboratory of the Institute of Geology and Seismology of the Academy of Sciences of Moldova. 20 stationary digital stations with a processing center in L'viv and six stations with a center in Chisinau operated in Ukraine and Moldova respectively. Different programs, local hodographs and magnitudes were used. The consolidated catalogue of earthquakes was created in L'viv. The total number of earthquakes in 2015 was NΣ=164 in the ranges: KR=4.7–12.2, h=1–160 km. The total seismic energy ΣE=5.381012 J. 23 earthquakes with depths h=50–160 km were located in the Vrancea zone. The maximum earthquake with KR=12.2 was registered on January 24 in the Vrancha mountains with hрР=89 km. In the Precarpathian region, nine events with energy classes KR=4.7–8.9 were registered, the total seismic energy of which is ΣЕ=1.25109 J. Increased seismic activity was observed in Transcarpathia. A series of tangible earthquakes with aftershocks was recorded in the Tyachiv area. Their total number was NΣ=77. The strongest tangible earthquake occurred in the area of Okrugla village on July 19 with KR=11.1. The earthquake source is located in the Earth's crust at a depth of h=7.7 km. The earthquake was felt by the population in the epicentral area with an intensity of I=6. In addition, this earthquake, like 5 others, was felt in the territory of northern Romania. In general, a decrease in the seismicity level in the Carpathians in 2015 was observed compared to that in 2013 and 2014.

SEISMICITY of AZERBAIJAN and ADJACENT TERRITORIES in 2015

In 2015, the network of Azerbaijan seismic stations included 35 digital stations, which continued to operate unchanged. The set of parameters determined for estimating the earthquake magnitude has decreased – determination of the MPVA magnitude and КР energy class has ceased. Only the local magnitude MLАзр was measured. The total number of earthquakes recorded by the Azerbaijan network of stations in 2015 amounted to 6419, however, only 128 of them with MLАзр3.0 are given in the catalogue of earthquakes of Azerbaijan published in the Appendix to this article. Seismic activity in the study area remained unchanged. The released seismic energy changed insignificantly compared to its value in 2014 and was close to the background level for the period 1993–2014. The increase in the number of earthquakes of the representative level (K≥8.6, MLАзр≥2.8) in comparison with the long-term average annual value is due to aftershocks of earthquakes on January 26 with MLАзр=4.9, June 3 with MLАзр=4.6, and September 4 with MLАзр=5.9. The 2015 most significant seismic event on the territory of the Republic was the earthquake on September 4 with MLАзр=5.9 and seismic intensity at the epicenter of I0=7.

A focal mechanism catalogue of earthquakes that occurred in the southeastern Alps and surrounding areas from 1928–2019

We present a focal mechanism catalogue of earthquakes that occurred in the southeastern Alps and surrounding areas from 1928 to 2019. The area involved in the process of convergence between the Adria microplate and Eurasia is one of the most seismically active regions in the Alpine Belt. The seismicity is minor, with the Ms= 6.5 Friuli earthquake being the strongest event recorded in the area, but the seismic risk is relevant because it is a highly populated region. For this reason, numerous studies have been carried out over time to investigate the stress field and the geodynamic characteristics of the region using focal mechanisms. To provide a comprehensive set of revised information, which is challenging to build quickly because the data are dispersed over many papers, we collected and revised the focal mechanisms that were previously published in the literature. Additionally, depending on the data quality and availability, we computed new focal mechanisms by first arrival polarity inversion or seismic moment tensor. Finally, we merged all the fault plane solutions to obtain a catalogue for a selection of 772 earthquakes with 1.8≤M≤6.5. For each earthquake, we reported all the available focal mechanisms obtained by different authors. We also suggested a preferred solution for users who need information provided expeditiously. The catalogue (https://doi.org/10.5281/zenodo.4660412; Saraò et al., 2021) is given as the Supplement of this paper and will be updated periodically (https://doi.org/10.5281/zenodo.4284970).

A focal mechanism catalogue of earthquakes that occurred in the southeastern Alps and surrounding areas from 1928–2019

We present a focal mechanism catalogue of earthquakes that occurred in the southeastern Alps and surrounding areas from 1928 to 2019. The area involved in the process of convergence between the Adria microplate and Eurasia is one of the most seismically active regions in the Alpine Belt. The seismicity is minor, with the Ms =thinsp;6.5 Friuli earthquake being the strongest event recorded in the area, but the seismic hazard is relevant because it is a highly populated region. For this reason, numerous studies have been carried out over time to investigate the stress field and the geodynamic characteristics of the region using focal mechanisms. To provide a comprehensive set of revised information, which is challenging to build quickly because the data is dispersed over many papers, we collected and revised the focal mechanisms that were previously published in the literature. Additionally, depending on the data quality and availability, we computed new focal mechanisms by first arrival polarity inversion or seismic moment tensor. Finally, we merged all the fault plane solutions to obtain a catalogue for a selection of 772 earthquakes with 1.8thinsp;≤thinsp;Mthinsp;≤thinsp;6.5. For each earthquake, we reported all the available focal mechanisms obtained by different authors. However, we also suggested a preferred solution for users who need expeditious information. The catalogue is available at https://doi.org/10.5281/zenodo.4284971 (Saraò et al., 2020).

Sismicidade do Nordeste do Brasil

ABSTRACTA revised catalogue of earthquakes, which occurred in the Northeastern region of Brazilup to 1980, is presented. Most of the data come from historical macroseismic informationcollected in old publications and newspapers. Recent instrumental data is used to deriveempirical relations between magnitude and felt area in order to estimate mb magnitudesfor the events not recorded by seismographic stations. Macroseismic data for two largeevents (Pereiro 23.02.68, and Pacajus 20.11.80) are presented in detail. Epicentres of fourrecent events recorded at NAT were determined by combining the macroseismic andinstrumental data and used to define a preliminary value of the ratio K=Vp/Vs = 1.77 forthe region under study. A swarm of activity at Parazinho, Rio Grande do Norte, wasstudied in more detail to estimate the parameter b of the Gutenberg and Richter frequency-relation.

SEISMOGENIC SOURCES IN THE AEGEAN AREA AND THEIR PREDICTIVE PROPERTIES

On the basis of all available information eight circular seismogenic sources, where shallow (h 100km) earthquakes occur, are defined in the broader Aegean area. The location of each source is further improved by optimization of the quasi-periodic properties of the strong (M≥6.0) instrumentally recorded mainshocks, identified in a complete catalogue of earthquakes (1911-2014) after declustering. Moreover, in the same seismogenic sources, all M≥6.3 mainshocks that comprise another complete catalogue (1850-2014) have also occurred. Interevent times of mainshocks generated in each source have predictive properties expressed by the TIMAPR (Time and Magnitude Predictable Regional) model whereas preshocks of recent mainshocks have also such properties expressed by the D-AS (Decelerating-Accelerating Seismicity) model. Retrospective prediction of the last mainshock in each source by the joint application of the two models resulted in reasonable uncertainties. Then, as a forward test, data up to the end of 2014 were used to predict the next expected mainshock in each of the eight sources and to identify the fault where its epicentre will probably be located.