Automatic Clustering of Macroseismic Intensity Data Points from Internet Questionnaires: Efficiency of the Partitioning around Medoids (PAM)

Abstract On the 6th of February 2016 at 11:00 hours local time (0900 UTC), KwaZulu-Natal was struck by an earthquake of local magnitude ML=3.8. The epicentre of the earthquake was located offshore in the Durban Basin. The earthquake shaking was widely felt within the province as well as in East London in the Eastern Cape province and was reported by various national media outlets. Minor structural damage was reported. A macroseismic survey using questionnaires was conducted by the Council for Geoscience (CGS) in collaboration with the University of KwaZulu-Natal (UKZN) which yielded 41 intensity data points. Additional intensity data points were obtained from the United States Geological Survey (USGS) Did You Feel It? programme. An attempt was made to define a local intensity attenuation model. Generally, the earthquake was more strongly felt in low-cost housing neighbourhoods than in more affluent suburbs.

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The autumn 1919 Torremendo (Jacarilla) earthquake series (SE Spain)

Annals of Geophysics ◽

10.4401/ag-6686 ◽

2015 ◽

Vol 58 (3) ◽

Author(s):

Josep Batlló ◽

José Manuel Martínez-Solares ◽

Ramon Macià ◽

Daniel Stich ◽

José Morales ◽

...

Keyword(s):

Intensity Data ◽

Similar Magnitude ◽

Se Spain ◽

Regional Seismicity ◽

Earthquake Series ◽

Data Points ◽

Instrumental Recording ◽

Definition Of ◽

Intensity Data Points ◽

Macroseismic Information

On 10th September 1919 several slightly damaging earthquakes struck the towns of Torremendo, Jacarilla (near Alicante, SE-Spain) and others nearby. Available magnitude estimations for the largest two events of the series are M = 5 approx. They were earthquakes of moderate size and they occurred in a region where similar magnitude earthquakes, thoroughly studied, occurred recently (1999 Mula; 2002 Bullas; 2005 La Paca; 2011 Lorca). This makes these events of interest for a better definition of the regional seismicity. We study their sources from the analysis of the available contemporary seismograms and related documents. A total of 23 seismograms from 9 seismic stations have been collected and digitized. These seismograms contain records for the two main events and several aftershocks of the earthquake series. Finally 44 files, corresponding to 44 recorded single component records from the different events have been processed. The events have been relocated and their magnitudes recalculated. Also, original macroseismic information for these events was recovered. A macroseismic evaluation of the series has been performed. Intensity data points have been recalculated and macroseismic location and magnitude obtained. We conclude that these are the largest earthquakes occurred in the region since the beginning of instrumental recording, with Mw = 5.5 for the largest shock, and that the available data could be compatible with a thrust mechanism related to blind faults in the Bajo Segura region.

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Intensity-distance attenuation laws for the Portugal mainland using intensity data points

Geophysical Journal International ◽

10.1093/gji/ggu317 ◽

2014 ◽

Vol 199 (2) ◽

pp. 1278-1285 ◽

Cited By ~ 4

Author(s):

Boris Le Goff ◽

José Fernando Borges ◽

Mourad Bezzeghoud

Keyword(s):

Intensity Data ◽

Data Points ◽

Intensity Data Points ◽

Attenuation Laws

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FITTING AN ELLIPSE TO THE SET OF INTENSITY DATA POINTS OF VRANCEA EARTHQUAKES

Journal of Engineering Studies and Research ◽

10.29081/jesr.v20i4.48 ◽

2016 ◽

Vol 20 (4) ◽

Author(s):

RASHID BURTIEV

Keyword(s):

Intensity Data ◽

Macroseismic Field ◽

Vrancea Earthquakes ◽

Test Criteria ◽

Data Points ◽

Set Of Points ◽

Intensity Data Points

Fitting an ellipse to the set of intensity data points of earthquakes occurred on 11.10.1940, 07.04.1977, 31.08.1986, 30.05.1990 and 31.05.1990 is performed. Test criteria indicate that the ellipse smoothes the observed line of macroseismic field. For all earthquakes, focal axes of 5, 6 and 7 EMS-98 intensity zones are directed along the y-axis. For other zones are oriented along the parallels. This fact is one more acknowledgement of the anisotropy of a geophysical medium. Approximation of the set of points with an ellipse is performed using the method proposed by Fitzgibbon.

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Re-evaluation of the macroseismic effects produced by the March 4, 1977, strong Vrancea earthquake in Romanian territory

Annals of Geophysics ◽

10.4401/ag-5641 ◽

2013 ◽

Vol 56 (1) ◽

Author(s):

Aurelian Pantea ◽

Angela Petruta Constantin

Keyword(s):

Seismic Event ◽

Seismic Intensity ◽

Intensity Data ◽

Large Area ◽

Macroseismic Field ◽

Vrancea Zone ◽

Macroseismic Effects ◽

Data Points ◽

Intensity Data Points ◽

Seismic Intensity Scale

In this paper, the macroseismic effects of the subcrustal earthquake in Vrancea (Romania) that occurred on March 4, 1977, have been re-evaluated. This was the second strongest seismic event that occurred in this area during the twentieth century, following the event that happened on November 10, 1940. It is thus of importance for our understanding of the seismicity of the Vrancea zone. The earthquake was felt over a large area, which included the territories of the neighboring states, and it produced major damage. Due to its effects, macroseismic studies were developed by Romanian researchers soon after its occurrence, with foreign scientists also involved, such as Medvedev, the founder of the Medvedev-Sponheuer-Karnik (MSK) seismic intensity scale. The original macroseismic questionnaires were re-examined, to take into account the recommendations for intensity assessments according to the MSK-64 macroseismic scale used in Romania. After the re-evaluation of the macroseismic field of this earthquake, the intensity dataset was obtained for 1,620 sites in Romanian territory. The re-evaluation was necessary as it has confirmed that the previous macroseismic map was underestimated. On this new map, only the intensity data points are plotted, without tracing the isoseismals.

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The 1895 Ljubljana earthquake: can the intensity data points discriminate which one of the nearby faults was the causative one?

Journal of Seismology ◽

10.1007/s10950-018-9743-z ◽

2018 ◽

Vol 22 (4) ◽

pp. 927-941

Author(s):

Lara Tiberi ◽

Giovanni Costa ◽

Petra Jamšek Rupnik ◽

Ina Cecić ◽

Peter Suhadolc

Keyword(s):

Intensity Data ◽

Data Points ◽

Intensity Data Points

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Reappraisal of the 1863 Huércal-Overa Earthquake (Betic Cordillera, SE Spain) by the Analysis of ESI-07 Environmental Effects and Building Oriented Damage

Geosciences ◽

10.3390/geosciences10080303 ◽

2020 ◽

Vol 10 (8) ◽

pp. 303

Author(s):

Pablo G. Silva ◽

Javier Elez ◽

Jorge L. Giner-Robles ◽

Raúl Pérez-López ◽

Elvira Roquero ◽

...

Keyword(s):

Environmental Effects ◽

Local Maximum ◽

Seismic Intensity ◽

Maximum Intensity ◽

Intensity Data ◽

Se Spain ◽

Epicentral Area ◽

Data Points ◽

Definition Of ◽

Intensity Data Points

This work reviews the 1863 Huércal-Overa earthquake (VI-VII EMS) based on the environmental seismic intensity scale (ESI-07) and oriented archaeoseismological building damage. The performed analysis identifies 23 environmental effects (EEEs) and 11 archaeoseismological effects (EAEs), completing a total of 34 intensity data-points within the intensity zone ≥ VI EMS. The new ESI intensity data quintuplicate the previous intensity data-points ≥ VI EMS (five localities) for this event. Sixteen of the identified EEEs indicate the occurrence of intensity VII-VIII within the Almanzora valley, south of Huércal-Overa, over an area of ca. 12–15 km2. Anomalies in water bodies, slope movements, hydrogeological anomalies, ground cracking, and other effects (gas emissions, tree shaking) are the more diagnostic EEEs—with one of them indicating a local maximum intensity of VIII-IX ESI-07 (Alboraija lake). Environmental earthquake damage of intensity ≥ VI covers an area of c. 100 km2, compatible with a VIII ESI intensity event. The spatial distribution of EEEs and EAEs indicates that the zone of Almanzora River Gorge, which was depopulated during the earthquake epoch, was the epicentral area, and compatible with seismotectonic data from active shallow blind thrusting beneath the Almagro Range. The use of ESI data in nearly unpopulated areas help to fill gaps between damaged localities (EMS data) multiplying intensity data-points, providing a better definition of the intensity zones and offering a geological basis to look for suspect seismic sources.

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Historical Earthquakes: New Intensity Data Points Using Complementary Data from Churches and Monasteries

Seismic Hazard and Risk Assessment - Springer Natural Hazards ◽

10.1007/978-3-319-74724-8_7 ◽

2018 ◽

pp. 103-116

Author(s):

Gheorghe Marmureanu ◽

Radu Vacareanu ◽

Carmen Ortanza Cioflan ◽

Constantin Ionescu ◽

Dragos Toma-Danila

Keyword(s):

Historical Earthquakes ◽

Intensity Data ◽

Data Points ◽

Intensity Data Points

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Macroseismic intensity data of the 22 April 2013 Tenk (Hungary) earthquake

Acta Geodaetica et Geophysica ◽

10.1007/s40328-014-0060-x ◽

2014 ◽

Vol 49 (3) ◽

pp. 283-294

Author(s):

Gyöngyvér Szanyi ◽

Zoltán Gráczer ◽

Erzsébet Győri

Keyword(s):

Macroseismic Intensity ◽

Intensity Data

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A Reappraisal of the Lurøy, Norway, Earthquake of 31 August 1819

Seismological Research Letters ◽

10.1785/0220190363 ◽

2020 ◽

Vol 91 (5) ◽

pp. 2462-2472 ◽

Cited By ~ 4

Author(s):

Päivi B. Mäntyniemi ◽

Mathilde B. Sørensen ◽

Tatiana N. Tatevossian ◽

Ruben E. Tatevossian ◽

Björn Lund

Keyword(s):

Historical Seismicity ◽

Macroseismic Intensity ◽

Macroseismic Data ◽

Sources Of Information ◽

Royal Swedish Academy ◽

Intensity Assessment ◽

Adequate Information ◽

Data Points ◽

Academy Of Sciences ◽

Written Sources

Abstract Archives and libraries were visited to find previously unknown documents testifying to the Lurøy, Norway, earthquake of 31 August 1819 in northernmost continental Europe. The focus here is on Sweden, Finland, and Russia, which are important for determining the area of perceptibility east of Norway. The new written sources include 12 notes or entries in original archived documents, six contemporary newspaper reports, and two recollections written down years later. The original documentation uncovered is contributory to establishing the authenticity of the observations in Finland and Sweden. The dates of the original documentation allow tracing of the dissemination of eyewitness accounts in writing from the inner area of perceptibility southward to the larger documentation and population centers. New sources of information include weather reports of the Royal Swedish Academy of Sciences, minutes of its meetings, and correspondence sent to the Senate in Finland. The minutes of meetings of the Academy indicate that ample data were collected in the Swedish province of Västerbotten. We found no original Russian documentation but uncovered national newspapers that are more reliable than the previously used Parisian newspaper. To increase transparency, we provide the first list of macroseismic data points (MDPs) including the respective documentation that testify to the Lurøy earthquake. A macroseismic intensity was assigned to a locality, using the European Macroseismic Scale of 1998, when adequate information was available. Accounting for the uncertainty of intensity assessment, the magnitude was estimated as moment magnitude M=5.9±0.2, reconfirming the ranking as the largest onshore or nearshore earthquake in the historical seismicity record of Fennoscandia. In addition to the reappraisal of the 31 August 1819 earthquake, a macroseismic map is provided for the earthquake of 17 February 1819, which was felt in northern Finland and Sweden. Some of its MDPs were previously associated with the Lurøy earthquake.

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