TY  - JOUR
A1  - Di Giacomo, Domenico
A1  - Bindi, Dino
A1  - Parolai, Stefano
A1  - Oth, Adrien
T1  - Residual analysis of teleseismic P-wave energy magnitude estimates: inter- and intrastation variability
JF  - Geophysical journal international
N2  - P>Computing the magnitude of an earthquake requires correcting for the propagation effects from the source to the receivers. This is often accomplished by performing numerical simulations using a suitable Earth model. In this work, the energy magnitude M(e) is considered and its determination is performed using theoretical spectral amplitude decay functions over teleseismic distances based on the global Earth model AK135Q. Since the high frequency part (above the corner frequency) of the source spectrum has to be considered in computing M(e), the influence of propagation and site effects may not be negligible and they could bias the single station M(e) estimations. Therefore, in this study we assess the inter- and intrastation distributions of errors by considering the M(e) residuals computed for a large data set of earthquakes recorded at teleseismic distances by seismic stations deployed worldwide. To separate the inter- and intrastation contribution of errors, we apply a maximum likelihood approach to the M(e) residuals. We show that the interstation errors (describing a sort of site effect for a station) are within +/- 0.2 magnitude units for most stations and their spatial distribution reflects the expected lateral variation affecting the velocity and attenuation of the Earth's structure in the uppermost layers, not accounted for by the 1-D AK135Q model. The variance of the intrastation error distribution (describing the record-to-record component of variability) is larger than the interstation one (0.240 against 0.159), and the spatial distribution of the errors is not random but shows specific patterns depending on the source-to-station paths. The set of coefficients empirically determined may be used in the future to account for the heterogeneities of the real Earth not considered in the theoretical calculations of the spectral amplitude decay functions used to correct the recorded data for propagation effects.
KW  - Time series analysis
KW  - Earthquake source observations
KW  - Body waves
KW  - Site effects
KW  - Wave propagation
Y1  - 2011
U6  - https://doi.org/10.1111/j.1365-246X.2011.05019.x
SN  - 0956-540X
VL  - 185
IS  - 3
SP  - 1444
EP  - 1454
PB  - Wiley-Blackwell
CY  - Malden
ER  - 
TY  - JOUR
A1  - Pilz, Marco
A1  - Parolai, Stefano
A1  - Stupazzini, Marco
A1  - Paolucci, Roberto
A1  - Zschau, Jochen
T1  - Modelling basin effects on earthquake ground motion in the Santiago de Chile basin by a spectral element code
JF  - Geophysical journal international
N2  - Simulations of strong ground motion within the Santiago de Chile Metropolitan area were carried out by means of 3-D deterministic wave propagation tool based on the spectral element method. The simulated events take into account the pronounced interface between the low-velocity sedimentary basin and the bedrock as well as topography of the area. To verify our model we simulated a regional earthquake recorded by a dense network installed in the city of Santiago for recording aftershock activity after the 2010 February 27 Maule main shock. The results proof the alluvial basin amplification effects and show a strong dependence of spectral amplification in the basin on the local site conditions. Moreover, we studied the seismic response due to a hypothetical M(w) = 6.0 event occurring along the active San Ramon Fault, which is crossing the eastern edge of the city. The scenario earthquakes exhibit that an unfavourable interaction between fault rupture, radiation mechanism and complex geological and topographic conditions in the near-field region may give rise to large values of peak ground velocity in the basin. Finally, 3-D numerical predictions of ground motion are compared with the one computed according to ground motion prediction equations selected among the next generation attenuation relationships, in terms of ground motion peak values and spectral acceleration. The comparison underlines that the 3-D scenario simulations predict a significantly higher level of ground motion in the Santiago basin, especially over deep alluvial deposits. Moreover, also the location of the rupture nucleation largely influences the observed shaking pattern.
KW  - Earthquake ground motions
KW  - Site effects
KW  - Wave propagation
KW  - South America
Y1  - 2011
U6  - https://doi.org/10.1111/j.1365-246X.2011.05183.x
SN  - 0956-540X
VL  - 187
IS  - 2
SP  - 929
EP  - 945
PB  - Wiley-Blackwell
CY  - Malden
ER  -