Calibration of IASPEI Standard Broad-band Magnitude mB for Iranian Plateau Earthquakes

نوع مقاله : مقاله پژوهشی

نویسندگان

1 M.Sc. Graduated, Department of Seismology, Institute of Geophysics, University of Tehran, Tehran, Iran

2 Associate Professor, Department of Seismology, Institute of Geophysics, University of Tehran, Tehran, Iran

چکیده

Iran, located in Alp-Himalayan belt and an active tectonic plate, is annually struck by major earthquakes. Since shallow earthquakes cause considerable loss of lives and property in this region, using any method to decrease the time of magnitude estimation of great earthquakes is very important for making a prompt decision about what to do. To achieve this aim, mB was computed as a rapid estimator for 38 earthquakes with magnitudes greater than 6 which occurred in Iran and adjacent areas (24°-44°N, 42°-66°E) from 1990 to 2018. The magnitudes estimated using calibration function by Bormann and Saul (2007) have a standard error of 0.49 from Mw (in this study). Therefore, mB’s calibration function was modified. As a result, the magnitudes obtained are approximately equal to those of reported Mw (a standard error of 0.18). The calibration function acquired in this study for Iran’s earthquakes was lower than the mB’s global calibration function which obtained by Saul and Bormann (2007). Their difference was nearly one unit at short distances. This difference can be related to the earthquakes located in subduction zones and plates boundaries used by Bormann and Saul (2007) which systemically have lower stress drops than intraplate earthquakes considered here and thus it’s needed to develop improved region-specific calibration functions for mB. However, the difference became smaller at distances greater than 20°. Consequently, this method and new calibration function can be employed to estimate magnitudes as early as possible across Iran plateau.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Calibration of IASPEI Standard Broad-band Magnitude mB for Iranian Plateau Earthquakes

نویسندگان [English]

  • Mehran Kiani 1
  • Ali Moradi 2
1 M.Sc. Graduated, Department of Seismology, Institute of Geophysics, University of Tehran, Tehran, Iran
2 Associate Professor, Department of Seismology, Institute of Geophysics, University of Tehran, Tehran, Iran
چکیده [English]

Iran, located in Alp-Himalayan belt and an active tectonic plate, is annually struck by major earthquakes. Since shallow earthquakes cause considerable loss of lives and property in this region, using any method to decrease the time of magnitude estimation of great earthquakes is very important for making a prompt decision about what to do. To achieve this aim, mB was computed as a rapid estimator for 38 earthquakes with magnitudes greater than 6 which occurred in Iran and adjacent areas (24°-44°N, 42°-66°E) from 1990 to 2018. The magnitudes estimated using calibration function by Bormann and Saul (2007) have a standard error of 0.49 from Mw (in this study). Therefore, mB’s calibration function was modified. As a result, the magnitudes obtained are approximately equal to those of reported Mw (a standard error of 0.18). The calibration function acquired in this study for Iran’s earthquakes was lower than the mB’s global calibration function which obtained by Saul and Bormann (2007). Their difference was nearly one unit at short distances. This difference can be related to the earthquakes located in subduction zones and plates boundaries used by Bormann and Saul (2007) which systemically have lower stress drops than intraplate earthquakes considered here and thus it’s needed to develop improved region-specific calibration functions for mB. However, the difference became smaller at distances greater than 20°. Consequently, this method and new calibration function can be employed to estimate magnitudes as early as possible across Iran plateau.

کلیدواژه‌ها [English]

  • mB
  • Mw
  • Earthquake Magnitude
  • Calibration
  • Iran Plateau