La profondità ipocentrale con metodi macrosismici



Aim of the present work is to determine the hypocentral depth of
an earthquake by macroseismic methods.
A short hystorical review of the main relations between macroseismic
intensity, acceleration and hypocentral depth from Cancani to the present time has been carried out. Particular care has been pointed out to
Kovesligethy and Blake works. Being the Blake's relation the basis of
all modern methods the y experimental value has been investigated to
apply in Italy in the formula
(/„ _ /„) = y log (Dn/h)
using some earthquakes with analitical depth known. There are singled
of two intermediate values of y; one (y ) valid for Italy in general
Y, = 4.382 ± 2.282
another (yc) more specific for central Italy
Y„ = 3.989 ± 1.344
From the investigation the AA. deem that the macroseismic method
cannot anyhow be applied, hence the AA. suggest the following application
1) for the isoseismals to be used (not more than three around the epic.)
2) for the hypocentral depths (only within the crust: h < 33 km)
3) for the y value (y < 7.0)
To determine quickly the depth (h + 5h), when the intermediate radii rc
of the circles equivalent to the I, II, III isoseismal areas of an earthquake
are been calculated (or measured), a table 3 has been calculated.
In table 4 both the macroseismic and the analitical depths relating
to untilized earthquakes, are compared.
The results obtained in the present work can be improved when the
researchers will have access to a greater lot of earthquakes with known
analitical depth and will be able to associate to a general intermediate
value Y, specific values of ± 5y; for each homogeneous structural unit.
In any case, the results obtained by that, as well by different macroseismic
methods, have always to retain approximate, even if the AA.
tried to furnish a range of indétermination to h values.

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Published by INGV, Istituto Nazionale di Geofisica e Vulcanologia - ISSN: 2037-416X