Determining earthquake epicentre from a single 3-component seismological station

An attempt has been made in this study to determine the epicentres by trigonometrical method from a single station using the three components of the ground's motion recorded by the Benioff Short Period Seismograph of the World Wide Standardized Seismograph Network (WWSSN) at Central Seismological Observatory (C.S.O.), Shillong. The trigonometrical method is based on the angle of bearing obtained from the ratio of the amplitudes of waves recorded on the horizontal components of the WWSSN seismograms. A comparison of recorded epicentres from the I.M.D. Seismological Network of Seismo, New Delhi with that of a single station i.e., C.S.O., Shillong has been made to estimate the accuracy of the method. The characteristics of the epicentral variations obtained from the Seismological Network of Seismo, New Delhi with that of C.S.O., Shillong are relatively small for local earthquakes compared to regional earthquakes with C.S.O., Shillong as the reference station. The characteristics of the epicentral variations particularly in the Shillong plateau are observed to be minimum. Strong correlations of epicentres are observed for both local as well as regional earthquake events.

Seismological Observatory Software: 30 Yr of SEISAN

The SEISAN software package for processing of earthquake data has been in use for 30 yr. SEISAN is a collection of programs that help to carry out tasks from the basic processing at a seismological observatory to more advanced seismological research. During its history, the software has been adopted to different hardware and operating systems. However, the core of the software with a folder- and files-based database and event-based processing has remained stable. The main focus in the design and development of the software has been the efficiency in data processing for the user. The software comes with manual, tutorial, and training exercises. This together with regular training activities has made SEISAN a useful tool for many observatories around the world.

The (Mythical) M 8.2 Off Coast of Peru Earthquake of 12 December 1908

Global earthquake catalogs covering the early twentieth century differ in their listings of a large earthquake, or earthquakes, on 12 December 1908. Some catalogs list an M∼7 earthquake originating in northern Myanmar (Burma) at ∼12:55 UTC on that date. Other catalogs do not list the Myanmar origin but list an earthquake with magnitude 8.2 originating in or near Peru at 12:08 UTC on the date. Some catalogs list both origins, but sometimes with additional evidence suggesting that the 1908 M 8.2 Peru origin may be “mythical.” In a review of arrival times of phases reported in seismic bulletins of 1908, conducted specifically to identify data that might be consistent with the sometimes‐cataloged Peru origin, we do not find a coherent set of such data. Many bulletin arrival times reported for 12 December 1908, however, are mutually consistent with the cataloged Myanmar origin. Comparisons of seismograms recorded at the Seismological Observatory of Göttingen in Germany (station GTT) on 12 December 1908 with seismograms obtained on the same instruments for later large earthquakes that are reliably located in Myanmar and Peru, respectively, are consistent with the implication of the bulletin arrival‐time observations. We conclude that a major earthquake did indeed occur in or near northern Myanmar on 12 December 1908 but that there was not on that date a great earthquake near Peru that would correspond to the sometimes‐cataloged M 8.2 Peru origin.

INSTRUMENTATION IN SEISMOLOGICAL OBSERVATORY – SKOPJE MONITORING AND DATA PROCESSING

The present activities in the field of earthquake seismology in Republic of North Macedonia are carried out by the Seismological Observatory at the Faculty of Natural Sciences and Mathematics, University "Sts. Cyril and Methodius" - Skopje, founded in 1957. Seismological Observatory in Skopje with telemetric network of digital seismological stations systematically monitors the seismic activity in the territory of Republic of North Macedonia and the bordering areas and also records the regional and teleseismic earthquakes. The instrumental seismological data at the Seismological Observatory in Skopje and at stations of its network have been always obtained by instrumentation which had followed the world trends. Actual scientific methods and, lately, the most sophisticated computer softwares have been used in analyses. Earthquakes with local magnitudes down to zero can be recorded and analyzed with the latest instrumentation by real time telemetric network data exchange and used softwares. The predominant hypocentral depths are less than 15 km. These data give opportunity for epicentral areas predefinition of the on the territory of Republic of North Macedonia, calculation of many source parameters and the mean velocity of the relative tectonic movement of the fault blocks, as well.

SEISMIC ZONES AND SEISMICITY OF THE TERRITORY OF THE REPUBLIC OF NORTH MACEDONIA

According to all sources of data available to the Seismological Observatory the seismic activity in the Republic of North Macedonia is mainly tectonic, with the exception of weak collapse earthquakes. This seismic activity is caused by its affiliation to the Mediterranean area of the Alpine-Himalayan orogeny belt. Epicentral areas belong to the three main seismic zones, West-Macedonian seismic zone, Vardar seismic zone and East-Macedonian seismic zone. Three secondary seismic zones, transverse to the main seismic zones, are also defined. Each of these zones is characterized by а specific time and space distribution of earthquake locations, with frequent seismic microactivity, lot of minor to light earthquakes and very rare moderate to major earthquakes. Observed seismic activity on the territory of the Republic of North Macedonia has a main role for the evaluation of the seismic hazard of the specific territory.

BRAZILIAN SEISMICITY: ONLINE NEWS AND SOCIAL MEDIA THAT HELP US

ABSTRACT. Historically, the earthquake studies was based on reports and records of newspapers, which referred to the estimation of the measure of the intensity of events. The advance of seismological instrumentation improved the calculation of magnitudes of earthquakes, which became a priority measure, to the detriment of intensity estimates. With the growth of access to information and communication technologies, the volume of relevant information for intensity estimation has become feasible and representative. We present the Brazilian Macroseismic Intensity Map between the years of 2006 to 2017, based on records of digital newspapers and blogs, and compare with the map of magnitudes recorded by the Brasília Seismological Observatory in the same period. The Brazilian Macroseismic Intensity Map contributes to the improvement of the Seismic Hazard Map. The results show the importance of preserving the information of seismic events published in digital media.Keywords: Macroseism, seismicity, intensity, digital newspapers, Brazilian Macroseismic Intensity Map.RESUMO. Historicamente, o estudo de terremotos era feito a partir de relatos e registros de jornais, que referenciam a estimativa da medida da intensidade dos eventos. O avanço da instrumentação sismológica aprimorou o cálculo das magnitudes dos terremotos, que tornou-se uma medida priorizada, em detrimento das estimativas de intensidade. Com o crescimento do acesso à informação e às tecnologias da comunicação, o volume de informações pertinentes para a estimativa da intensidade tornou-se viável e representativo. Apresentamos o Mapa Brasileiro de Intensidade Macrossísmica entre os anos de 2006 a 2017, baseado em registros de jornais digitais e blogs, e comparamos com o mapa de magnitudes registradas pelo Observatório Sismológico de Brasília no mesmo período. O Mapa Brasileiro de Intensidade Macrossísmica contribui para a melhora o Mapa de Risco Sísmico. Os resultados indicam a importância de preservar a informação de eventos sísmicos publicados em mídias digitais. Palavras-chave: Macrossismo, sismicidade, intensidade, jornais digitais, Mapa Brasileiro de Intensidade.

Análisis de la actividad volcánica tipo VT y LP del volcán Nevado del Ruiz entre 1985-2012 [Analysis of volcanic activity type VT and LP of the Nevado del Ruiz volcano between 1985-2012]

En la Cordillera de los Andes existen varios complejos volcánicos, siendo el Complejo volcánico Cerro Bravo – Cerro Machín (CVCBCM), el más septentrional de ellos. El Volcán Nevado del Ruiz (VNR), ubicado en dicho complejo, está activo y su evento más devastador fue el ocurrido en noviembre 13 de 1985, cuando el flujo de lodo originado tras el deshielo parcial del casquete glaciar, producto de una erupción freato-magmática, arrasó la población de Armero (Tolima), con un saldo de 23000 personas muertas. Como respuesta a tal catástrofe, se creó el Observatorio Vulcanológico y Sismológico de Manizales, que lleva ya 27 años de constante monitoreo de la actividad de los volcanes del CVCBCM, para lo cual utiliza varias técnicas geofísicas, geodésicas y geoquímicas. Este trabajo tiene como objetivo mostrar la actividad del volcán a partir de la sismicidad, considerando el conteo de eventos sísmicos y la energía liberada por los mismos, diferenciando los sismos fractura y los de movimiento de fluidos. La labor de clasificación y lectura de los sismos, cuenta con la participación activa de estudiantes de pregrado, fungiendo como asistentes de investigación, lo que les permite colaborar en la vigilancia volcánica y adquirir conocimientos dirigidos a su futuro desempeño como vulcanólogos.Palabras claves: Monitoreo volcánico, sismicidad, sismos de fractura, sismos de movimiento de fluidosIn the Andes there are several volcanic complexes, with the Volcanic Complex Cerro Bravo - Cerro Machin (CVCBCM), the northernmost of them. The Nevado del Ruiz volcano (VNR) located in said complex, is active and was the most devastating event occurred in November 13, 1985, when the mudflow caused after partial melting of the ice cap, the result of an eruption freato- magmatic, razed the town of Armero (Tolima), leaving 23,000 people dead. In response to this catastrophe, the Volcanological and Seismological Observatory of Manizales, which has been 27 years of constant monitoring of the activity of the volcanoes of CVCBCM, for which utilizes various geophysical, geodetic and geochemical techniques was created. This work aims to show the volcano seismicity from considering counting seismic events and the energy released by them, differentiating the fracture earthquakes and fluid motion. The work of sorting and reading earthquakes, with the active participation of undergraduates, serving as research assistants, allowing them to collaborate in volcano monitoring and acquire knowledge aimed at their future roles as volcanologists.Keywords: Volcanic Monitoring, seismicity, seismic fracture fluid motion earthquakes

Descubrimiento de Reglas de Asociación de eventos eruptivos del volcán Galeras [Discovery of Association Rules from eruptive events of Galeras volcano]

En este artículo se presentan los primeros resultados del proyecto de investigación que tuvo como objetivo detectar patrones de eventos eruptivos del volcán Galeras con técnicas de minería de datos, a partir de los datos almacenados en el Observatorio Vulcanológico y Sismológico de Pasto - OVSP (Colombia), aplicando la metodología CRISP-DM. Se construyó, limpió y transformó un repositorio de datos con la información de los eventos eruptivos del volcán Galeras registrados desde 1989 hasta 2013. A partir de este repositorio, se detectaron patrones asociados a estos eventos, utilizando la tarea de minería de datos asociación. El conocimiento generado se integrará al existente con el fin de ayudar al OVSP y a los organismos gubernamentales de prevención de desastres a tomar decisiones eficaces en lo relacionado a la implementación de planes de prevención ante una posible erupción del volcán Galeras.Palabras Clave: Patrones de Eventos Eruptivos, Volcán Galeras, Minería de DatosIn this paper, the first results of a research project that aimed to detect patterns of eruptive events of Galeras volcano with data mining techniques from the data stored in the Volcanological and Seismological Observatory of Pasto - VSOP (Colombia), applying CRISP-DM methodology, are presented. A data repository with the information of the eruptive events of Galeras volcano recorded from 1989 to 2013 was built, cleaned and transformed. Using the data mining task association were detected patterns associated with these events. The knowledge generated will be integrated to the existing order to help VSOP and government agencies of disaster prevention to take effective decisions related to the implementation of prevention plans for a possible eruption of the Galeras volcano.Keywords: Patterns of eruptive events, Galeras volcano, Data Mining.

AFORS - Autonomous Fiber Optic Rotational Seismograph as a System for Continuous Monitoring the Rotational Seismic Events

We outline the development and application of the Autonomous Fibre-Optic Rotational Seismograph (AFORS), which utilizes the Sagnac effect for a direct measurement of seismic rotation. The main advantage of AFORS is it complete insensitivity to linear motions as well as a direct measurement of rotational components emitted during seismic events. The presented system contains a special autonomous signal processing unit which optimizes its operation for the measurement of rotation motions, whereas applied telemetric system based on the Internet allows for a remote AFORS control. The laboratory investigation of the two such devices indicated they keep accuracy no less than 5.1·10-9to 5.5·10-8rad/s in the frequency bandpass from 0.83 Hz to 106.15 Hz with protect linear changes of sensitivity in above bandpass. The experimental results of AFORS-1 application for continuous monitoring the rotational events in the Książ (Poland) seismological observatory are also presented.