TITLE:
First Determination of Source Parameters of Moderate Earthquakes (4.1 ≤ M ≤ 5.1) in Morocco from Spectral Analysis
AUTHORS:
Ihsane Bensaid, Lahcen Bahi, Fida Medina
KEYWORDS:
Morocco, Seismicity, Fault-Plane Solutions, P-Wave Spectra, Source Parameters, Seismotectonics
JOURNAL NAME:
Open Journal of Earthquake Research,
Vol.3 No.2,
May
29,
2014
ABSTRACT:
Recent installation of an array of broad band seismological stations in Morocco allowed us to study the records of five recent (2005-2008) moderate earthquakes (4.1 ≤ M ≤ 5.1) in order to determine their source parameters (seismic moment, fault slip, rupture area and stress drop) from P-wave spectra. We also studied the older Rissani events of 1992 using teleseismic data. Values of Mo, r, Δu and Δσ are, respectively, 1.1 × 1013 - 6 × 1016 Nm; 0.50 - 3.9 km; 0.8 - 5.8 cm and 0.3 - 1.49 MPa. The results are in accordance with the seismotectonic and geodynamic setting of Morocco as, for instance, the amount of slip along the faults with respect to the relative displacement of Nubia to Iberia (~4 mm·yr-1) determined from GPS data, taking into account the period of stress accumulation. However, some events show very variable corner frequency and low-frequency amplitude values which lead to considerably higher stress drop and fault slip values, especially at the nearest stations, which may reflect some site effects or uncertainties on depth and take-off angles.