Intensity and isoseismal map of 25th November 2007 Delhi earthquake

An earthquake of magnitude ML: 4.3 occurred on 25th November 2007 (2312 UTC) in Delhi with hypocenter at 28.56° N / 77.08° E and focal depth 33.1 km. The epicenter was at about 21 km SW of Delhi University. It was widely felt in and around Delhi and created panic among the local populace. A macroseismic survey was conducted in about ten days starting from 27th November, 2007 at 89 locations covering an area of about 1500 sq. km in Delhi and its neighborhood through a questionnaire. The results of the macroseismic survey allowed establishment of spatial distribution of the earthquake effects in the form of isoseismal map generated using geo-statistical analysis tool of ArcGIS 9.1. The isoseismal map shows that most parts of Delhi region experienced an intensity of V on MMI scale, except on northern most region of Delhi where intensity was found IV. The mean isoseismal radii for the zones V, IV, III and II are 29.13, 57.78, 83.63 and 100.75 km, respectively. The orientation of elongated epicentral track of intensity field shows that the stress release was pronounced along Delhi-Sargodha ridge and earthquake was attributed to activities of this ridge.

SEISMICITY of TAJIKISTAN and ADJACENT TERRITORIES in 2015

The seismic monitoring system consisting of seven digital stations continued to operate in Tajikistan in 2015. This network has registered 9071 earthquakes with KR=8.6–17.0, 6427 of which were Pamir-Hindu Kush earthquakes with intermediate depths (h=70–300 km), and 2644 were shallow events. The total seismic energy released was E=1.8151017 J. The strongest for 2015 was the Hindu Kush earthquake on Octo-ber 26 with Mw=7.5, h=230 km (hpP=217 km) that occurred near the southern borders of the Republic. This earthquake caused significant damage and the death of at least 115 people. It was felt on the territory of 14 states, with a total shaking area of more than 14106 km2. A detailed isoseismal map of this earthquake is given for the Tajikistan territory only. The earthquake was accompanied by a series of over 1400 aftershocks with KR=8.6–12.8, unexpectedly numerous for a deep earthquake. Within the borders of the Republic, the Sarez-II earthquake occurred near the Lake of Sarez on December 7 with Mw=7.2, h=20 km, I0=8, was the strongest one. Undoubtedly, it was triggered by the Hindu Kush earthquake on October 26. In total, more than 500 houses were damaged, dozens of people were injured, and there were human casualties. A detailed isoseismal map of this earthquake was made for four levels of intensity – I=7, 6, 5 and 4. The number of its aftershocks for 24 days only was 1342, with KR=8.6–13.9. As a result the level of seismicity in Tajikistan in 2015, both in terms of the number of earthquakes and the level of released seismic energy, was the highest during the period of instrumental observations.

Correlation Of Residual Anomaly and Isoseismal Map by Using Power Spectral Density Method in Palu City Region

This research was conducted to see the correlation between residual anomaly map, geological map, and isoseismal map and how they contribute to the determination of earthquake-prone areas. Moreover, the area studied is an area that is difficult to obtain geophysical data such as urban areas. The residual anomaly is obtained by calculating the bouguer anomaly from elevation data and free-air correction satellite, which then through the FFT process changes the spatial domain to the frequency domain in MATLAB. Thus, it can separate regional anomaly maps with residuals. Using the overlaying technique on two maps, namely residual anomaly maps with isoseismal, a clear correlation was found between the residual anomaly value and the impact of the earthquake as well as the validation of the geological map in the area

Intensity of Induced Earthquakes in Northeast British Columbia, Canada

The damage potential of induced earthquakes associated with fluid injection is a major concern in hydrocarbon resource development. An important source of data for the assessment of damage is macroseismic intensity perceived by people and structures. In the Western Canada Sedimentary Basin (WCSB) where the occurrence of seismicity is mostly related to oil and gas activities, the collection of intensity data is incomplete. In this study, we present a comprehensive dataset gathered by the BC Oil and Gas Commission in the period 2016–2020. We assign intensities to individual felt reports according to the modified Mercalli intensity (MMI) scale and associate each MMI value to an earthquake. The isoseismal map of the largest earthquake in the Septimus region of northeast British Columbia is also provided using the compiled intensity dataset complemented with data from the U.S. Geological Survey and Natural Resources Canada “Did You Feel It?” systems along with the intensities converted from ground-motion amplitudes. We consider an approximate 10 km radius around the mainshock of 30 November 2018 earthquake with moment magnitude of 4.6 to be the meizoseismal area based on maximum intensities of 4–5. We also investigate the distance decay of intensity for shallow induced earthquakes in comparison with deeper natural events with the same magnitudes. Although intensities from shallow earthquakes (depth≤5 km) can be higher than deep events (depth≥10 km) at close distances (10–15 km), they tend to decrease abruptly at greater distances to become lower than deep events. The localization of large intensities from induced earthquakes within the meizoseismal area warrants special attention in future resource developments and call for systematic intensity data collection in the WCSB.

KAJI-SAIEARTHQUAKEonNovember 14, 2014 withКР=13.7, Mw=5.4, I0=7 (Kyrgyzstan, SouthernIssyk-Kul’)

Information on the earthquake with Mw=5.4 that occurred on the southern coast of the Issyk-Kul lake on the southwestern slope of the Tegerek mountains (Kyrgyzstan) on November 14, 2014 is given. The epicenter is located in the Jumgalo-Terskey zone, identified as the Tonsky block, in which felt earthquakes with intensity up to 7 have occurred repeatedly. 231 aftershocks were recorded in the first day, in the second day – 13 aftershocks, then seismic activity decreased. Most of the aftershocks are localized in the depth range of 17–21 km, close to the depth of the main shock (h=20 km). The earthquake had the reverse fault type. Macroseismic survey was fulfilled only in the epicentral zone due to the complex weather conditions (late autumn, highlands). The theoretical isoseismal map was created for receiving the more complete picture of the earthquake impact outside of its epicentral zone.

SPITAK-V EARTHQUAKE on July 6, 2014 with МL=4.0, I0=5–6 (Armenia)

The work presents the results of macroseismic survey of the Spitak-V earthquake which occurred on July 6, 2014 with МL=4.0, I0=5–6 in the focal zone of the destructive Spitak earthquake 1988 with I0=10. The isoseismal map of the July 6, 2014 earthquake was made and the focal mechanism parameters were determined. According to the focal mechanism decision, the movement in the source was a strike-slip with minor uplift components.

KARAGANDA (KARABASS) EARTHQUAKE onJune 21, 2014, KP=11.7, MS=4.0, I0р=5 (Central Kazakhstan)

The work shows the results of macroseismic analysis of the earthquake with mb=5.2 occurred near Karaganda on June 21, 2014 and recorded by seismic stations of the Institute of Geophysical Research ME RK. Basing on the data of macroseismic examination that included acquisition and analysis of information on the dam-aged houses and industrial buildings, the shaking intensity on MSK-64 scale was estimated for 34 settlements on the territory of ≈100 km radius around the earthquake epicenter. For the Karaganda earthquake localized in the area that was previously considered aseismic the basic parameters is studied, the focal mechanism is constructed, and the isoseismal map is compiled. Basing on the analysis of seismic records, focal mechanism and geological and tectonic features of the region, it was concluded that the natural-induced nature of the earthquake is most probable.

A sismicidade no Curso de Sismologia (1970) de Frederico Machado e seis cartas históricas de isossistas com interesse para o Ensino de Ciências

Resumo Nos documentos curriculares portugueses em vigor para a disciplina de Ciências Naturais, 7.o ano de escolaridade, há uma orientação no sentido da exploração e discussão de cartas de isossistas relativas a sismos com efeitos no território nacional. Neste trabalho incluímos alguns apontamentos históricos sobre o conceito de intensidade sísmica, a qual permite a medição de um terramoto sem recurso a instrumentos, e apresentamos seis cartas de isossistas que constam no Curso de Sismologia (1970) de Frederico Machado. Para cada carta de isossistas analisámos as fontes utilizadas pelo autor e produzimos uma reflexão com sugestões para exploração em contexto didático. Verificámos que estas cartas são representativas da sismicidade no território português e constituem uma oportunidade para explorar o conceito de intensidade sísmica e corresponder às orientações curriculares (ensino básico) para este tema. Palavras-chave: História da Sismologia, intensidade sísmica, cartas de isossistas Abstract In current portuguese curricular documents for the Natural Sciences subject, 7th grade, there is an orientation towards exploring and discussing isoseismal maps related to earthquakes with effects in the portuguese territory. In this work we include some historical notes about the concept of seismic intensity, which allows the measurement of an earthquake without the use of instruments, and we present six isoseismals maps that are included in Curso de Sismologia (1970) by Frederico Machado. For each isoseismal map we analyzed the sources used by the author and we produced a reflection with suggestions for didactic exploration. We found that these maps are representative of the seismicity in the Portuguese territory and provide an opportunity to explore the concept of seismic intensity and to meet the curricular orientations (basic education) for this theme. Keywords: History of Seismology, seismic intensity, isoseismal maps

MARJANBULAK EARTHQUAKE on MAY 25, 2013 with КР=14.1, МS=5.2, I0=7 (Djizakh province, Uzbekistan)

The instrumental data and the results of the macroseismic survey of the Marjanbulak earthquake MwMOS=6.2 with an intensity of 8 on the MSK-64 scale, which occurred in Uzbekistan, are presented. The isoseismal map is given. Correspondence between the intensity of the earthquake manifestation and the regional macroseismic field equation is shown. Geological and geophysical, engineer-geological conditions in the epicentral zone are described. The seismicity of the observation area is reviewed.

TUYABUGUZ EARTHQUAKE on May 25, 2013 with КР=14.1, МS=5.2, I0=7 (Tashkent district, Uzbekistan)

The results of instrumental and macroseismic observations of the Tuyabuguz earthquake on May 24, 2013, with КР=14.1, МS=5.2, I0=7 (MSK-64) are presented. The earthquake occurred 35 km southwest of Tashkent and was felt up in many settlements of Uzbekistan. The isoseismal map is given. Correspondence between the intensity of the earthquake manifestation and the regional macroseismic field equation is shown. Geological and geophysical conditions in the epicentral zone are described. The seismicity of the observation area is reviewed. The focal area of the Tuyabuguz earthquake is located in the seismically active zone, where strong historical and instrumentally recorded events occurred with intensity I=7–8 point.