A major earthquake, with magnitude Mw 7.3, struck Sarpol Zahab (Kermanshah province, Iran) on November 12, 2017, causing extended damage and casualties. The epicenter was located in the Northwestern part of the Zagros mountain range, an active belt originated by the Arabia-Eurasia collision. We explore seismicity preceding this earthquake, by using the Iranian Seismological Center instrumental earthquake catalog (IGTU), with the aim to identify possible anomalies in background seismicity that can be related with this and other future large events. For this purpose, we used a method for intermediate term forecasts of large earthquakes, namely the Region Time Length (RTL) algorithm, which analyzes declustered catalogs and is sensitive to quiescences that may precede major earthquakes. RTL has been progressively refined and has been applied in several regions worldwide during the last decades. To decluster the earthquake catalog we used a quite novel approach, based on the nearest-neigbour distances between events in the space-time-energy domain, a method that preserves the background seismicity while removing the clustered component. The retrospective application of RTL algorithm to the area surrounding the mainshock epicenter highlights two significant quiescences: one preceding the Sarpol Zahab Mw 7.3 earthquake, and the other occurring before a Mw 5.7 earthquake, which struck the same region on November 2013. The quiescences duration ranges from few months to one year and is compatible with earlier results from different regions of the world. In addition, we applied an enhanced variant of RTL algorithm, which allows us drawing maps for the whole study region and that shows only quiescences consistently detected for different choices of the free parameters, and hence more stable. The resulting map for Northwestern Iran, calculated for the time span 1 June 2017–11 November 2017, evidences two broad quiescence regions, oriented NW-SE along the Zagros belt. One, located to the north, evidences a significant seismic anomaly corresponding to the Sarpol Zahab earthquake, which disappeares immediately after the event. The second one, located in the southeastern part of the study region, persists up to the end of the available catalog (October 4, 2018).

A seismic quiescence before the 2017 Mw 7.3 Sarpol Zahab (Iran) earthquake: Detection and analysis by improved RTL method

Gentili S;Peresan A;
2019

Abstract

A major earthquake, with magnitude Mw 7.3, struck Sarpol Zahab (Kermanshah province, Iran) on November 12, 2017, causing extended damage and casualties. The epicenter was located in the Northwestern part of the Zagros mountain range, an active belt originated by the Arabia-Eurasia collision. We explore seismicity preceding this earthquake, by using the Iranian Seismological Center instrumental earthquake catalog (IGTU), with the aim to identify possible anomalies in background seismicity that can be related with this and other future large events. For this purpose, we used a method for intermediate term forecasts of large earthquakes, namely the Region Time Length (RTL) algorithm, which analyzes declustered catalogs and is sensitive to quiescences that may precede major earthquakes. RTL has been progressively refined and has been applied in several regions worldwide during the last decades. To decluster the earthquake catalog we used a quite novel approach, based on the nearest-neigbour distances between events in the space-time-energy domain, a method that preserves the background seismicity while removing the clustered component. The retrospective application of RTL algorithm to the area surrounding the mainshock epicenter highlights two significant quiescences: one preceding the Sarpol Zahab Mw 7.3 earthquake, and the other occurring before a Mw 5.7 earthquake, which struck the same region on November 2013. The quiescences duration ranges from few months to one year and is compatible with earlier results from different regions of the world. In addition, we applied an enhanced variant of RTL algorithm, which allows us drawing maps for the whole study region and that shows only quiescences consistently detected for different choices of the free parameters, and hence more stable. The resulting map for Northwestern Iran, calculated for the time span 1 June 2017–11 November 2017, evidences two broad quiescence regions, oriented NW-SE along the Zagros belt. One, located to the north, evidences a significant seismic anomaly corresponding to the Sarpol Zahab earthquake, which disappeares immediately after the event. The second one, located in the southeastern part of the study region, persists up to the end of the available catalog (October 4, 2018).
File in questo prodotto:
File Dimensione Formato  
Gentili_et_al_2019.pdf

non disponibili

Tipologia: Altro materiale allegato
Licenza: Non specificato
Dimensione 3.25 MB
Formato Adobe PDF
3.25 MB Adobe PDF   Visualizza/Apri   Richiedi una copia

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/20.500.14083/1927
 Attenzione

Attenzione! I dati visualizzati non sono stati sottoposti a validazione da parte dell'ateneo

Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 5
  • ???jsp.display-item.citation.isi??? 6
social impact