La profondità ipocentrale con metodi macrosismici

Abstract

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