- Ground-motion model is:
where Y is in cm∕s2, C14 = 5.57, C22 = 0.82, C31 = -1.59, C43 = -0.14, C54 = -0.18 and σ = 0.68.
Assume 15km inside ln(R + …) from Theodulidis and Papazachos (1992).
- Use two site categories:
S = 0
- Rock: includes stiff sites.
S = 1
- Alluvium: includes both shallow and deep soil sites.
- Use two source mechanism categories:
F = 0
- Thrust and strike-slip earthquakes.
F = 1
- Normal earthquakes.
- Use epicentral distance because in Italy and Greece the surface geology does not show any evident faulting,
consequently it is impossible to use a fault distance definition.
- Good distribution and coverage of data with respect to site category and source mechanism.
- Consider six strong-motion records (three Italian and three Greek) with different associated distances,
magnitudes and record length and apply the different processing techniques of ENEA-ENEL and ITSAK
to check if data from two databanks can be merged. Digitise six records using same equipment.
ITSAK technique: subtract the reference trace (either fixed trace or trace from clock) from uncorrected
accelerogram and select band-pass filter based on either Fourier amplitude spectra of acceleration
components or selected using a different technique. ENEA-ENEL technique: subtract the reference trace
from uncorrected accelerogram and select band-pass filter by comparing Fourier amplitude spectra of
acceleration components with that of fixed trace. Find small differences in PGA, PGV, PGD so can merge
Italian and Greek data into one databank.
- Use four step regression procedure, similar to that Theodulidis and Papazachos (1992) use. First step use
only data with M ≥ 6.0 (7 ≤ R ≤ 138km) for which distances are more accurate to find geometrical
coefficient C31. Next find constant (C12) and magnitude (C22) coefficients using all data. Next find constant
(C13) and soil (C43) coefficients using all data. Finally find constant (C14) and source mechanism (C54)
coefficients using data with M ≥ 6.0 for which focal mechanism is better constrained; final coefficients are
C14, C22, C31, C43 and C54. Investigate influence of distance on C54 by subdividing data in final step into
three categories with respect to distance (7 ≤ R ≤ 140km, 7 ≤ R ≤ 100km and 7 ≤ R ≤ 70km).
- Equation intended as first attempt to obtain attenuation relations from combined databanks and site
characteristics and fault rupture properties could and should be taken into account.