8/10/2019 12 Baglioni Et Al 2013

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Isostatic rebound at the footwall of a low-angle normal fault

in the Northern Apennines of Italy.

Baglioni S., Mirabella F., Lupattelli A., Pauselli C.

Dip. Scienze della Terra, Universit di Perugia, Piazza Universit !, "#!$% Perugia, &tal'

9th Topo-Europe Workshop - Certosa di Pontignano, Italy, 9-11 October 21!

Abstract

Man' e(tensional )ault s'ste*s, at t+e regional scale, are driven b' ver' lo dipping -"%"/0

nor*al )aults, loangle nor*al )aults -LA1Fs0 or e(tensional detac+*ents.

2eological evidence and seis*ic re)lection pro)iles suggest t+at LA1Fs acco**odated a

signi3cant a*ount o) crustal e(tension and t+at t+e' can be active and release eart+4ua5es.

Suc+ )aults co**onl' unroo) *idcrustal levels, and t+e resulting buo'anc' )orces cause isostaticad6ust*ent b' upli)t o) t+e )ootall.

T+e Alto Tiberina )ault -ATF0, in t+e nort+ern Apennine, is an e(a*ple o) an active loangle

nor*al )ault. T+e ATF e(tends in t+e 117SS8 direction )or 9" 5* and it is dipping 818: it +as an

average dip o) $"/ and a t'pical staircase tra6ector'. 2PS and seis*ological data s+o t+at t+is )ault

is active, and causes *icroseis*icit'.

T+e geological sections obtained b' seis*ic re)lection pro)iles, s+o t+e presence o) a do*e

s+aped structure, it+ a avelengt+ around !" 5*, in t+e )ault )ootall: t+e' also s+o t+at t+e

ATF )ault )lattens to +orizontal near t+e sur)ace. T+e latest +'pot+eses suggest t+at t+is

con)iguration can be due to t+e isostatic )ootall upli)t o) t+e )ault.

&n t+is or5, t+e isostatic response +as been e(a*ined, as a conse4uence o) t+e tectonic denudation

due to t+e action o) t+e Alto Tiberina )ault, b' e*plo'ing t+e isostatic )le(ural t+eor'. T+is t+eor'

ta5es in consideration t+e de)lection o) an elastic la'er above a viscous la'er.

T+e para*eters t+at *ost a))ect t+e isostatic upli)t are; t+e inclination o) t+e nor*al )ault, t+e

5*, t+at corresponds to a lo

seis*ic pave velocit' la'er, and to t+e loer border o) t+e *a6orit' o) eart+4ua5es distribution in

t+e studied area.