Active and capaci faults

23 MAGGIO - VERSO UN AGGIORNAMENTO DEGLI INDIRIZZI E CRITERI PER LA
MICROZONAZIONE SISMICA
Faglie attive e capaci
Active and capable faults
P. Boncio
Università “G. d’Annunzio” di Chieti-Pescara (Ud’A)
[email protected]
G. d’Annunzio
Chieti-Pescara
Definition in “Indirizi e Criteri per la Microzonazione Sismica 2008”
Faglia attiva e capace
Faglia per la quale esistono evidenze di ripetuta riattivazione negli
ultimi 40.000 anni (parte alta del Pleistocene superiore Olocene) e capace di rompere la superficie topografica.
Active and capable fault
Fault with evidence of repeated reactivation during the last 40,000
years (upper part of Late Pleistocene - Holocene) and capable of
rupturing the ground surface.
Boncio et al. – Surface Fault Rupture Hazard (SFRH) Zoning
Active normal fault
In Italy…
… it is known that some existing buildings
or critical facilities are exposed to
Surface Fault-Rupture Hazard.
The 2009 L’Aquila earthquake (M 6.3) in
central Italy brought back to the
attention this still unsolved problem in
Italian regulations.
Why a PROBLEM ?
The Italian regulations
“Norme tecniche
per le costruzioni”
(NTC 08)
D.M. 14 gennaio 2008
(G.U. n. 29 del 4.02.2008 suppl.
ord. n° 30)
7.11.3.1 Local seismic response
7.11.3.2 Stratigraphic amplification
7.11.3.3 Topographic amplification
7.11.3.4 Liquefaction
7.11.3.5 Slope stability
… and the SFRH ??
Why a PROBLEM ?
Legend of:
“Carta delle microzone
omogenee in prospettiva
sismica (LIVELLO 1)”
“ … only active and
capable faults
recognized by experts
(e.g., in scientific
publications).”
Working Group MS, 2008
Why a PROBLEM ?
Norcia case study
(Galli et al., 2005; Gruppo di
Lavoro MS Norcia, 2006)
Working Group MS, 2008
A “reference” document for Surface Fault-Rupture Hazard
• Main purpose: prevent the construction of buildings
for human occupancy on the surface trace of active
faults.
• The A-P EFZ Act requires the State Geologist to
establish regulatory zones around the surface traces
of active faults (Earthquake Fault Zones).
• The EFZs vary in
width.
The boundaries are
placed 150-200 m
away from traces of
major active faults;
Since 1972, last revision 2007
• Local agencies must regulate most development
projects (new or renewed constructions) within
the zones. Before a project can be permitted, cities
and counties must require a geologic investigation
to demonstrate that proposed buildings will not be
constructed across active faults.
• If an active fault is found, a structure for human
occupancy must be SET BACK from the fault,
generally 50 feet (15 m), unless proven otherwise.
60 to 90 m away from
well-defined, minor
faults.
EFZ
Exceptions exist where
faults are complex or
not vertical.
State of the art in ITALY
Problems
• The national regulations (i.e. NTC08) lack of specific
recommendations against Surface Fault-Rupture Hazard.
• In “Indirizzi e Criteri per la MS (Working Group MS,
2008)” there is not distinction between Earthquake
Fault Zones and Fault Setbacks and general criteria in
defining the shape and width of the zones are not
explicated.
Towards an improvement of “Indirizzi e Criteri per la Microzonazione Sismica”
Data from world-wide normal faulting earthquakes
Earthquake
1915 Avezzano,
Italy
M
7.0
Fault
Fucino system
Kinematics SRL (km)
N
1915 Pleasant
Valley, USA
7.6
China Mt., Tobin,
Pearce, Sou Hills
N
1946 Ancash, Peru
6.8
Quiches
N
1950 Fort Sage
Mts., USA
5.6
Fort Sage Mts.
Fairview Peak
West Gate
1954 Fairview
Peak, USA
Gold king
Phillips Wash
1959 Hebgen Lake,
USA
6.8
Dixie Valley
5.8(v)
21
WRZ (m)
1* - 5 (1);
1* - 40 (2)
8.85
source
GG99
1* - 195 (mostly
≤ 120) (1);
750 - 1350 (2)
Wa84
1* - 70
Be91
3.5(v)
0.2(v)
1* - 380
M = 5.6 – 7.6
Gi57
31.6
3.8(v) 2.9(h)
1* - 1010
(mostly ≤ 150)
Ca96
10
1.1(v) 1.2(h)
1* - 85
Ca96
1* - 120
Ca96
RN
14
0.8(v) 1.7(h)
1* - 40
Ca96
N
8.5
1.0(v)
1* - 580
Ca96
LN
6.2
0.5(v) 0.8(h)
N
42
2.8(v)
1* - 400 (mostly
≤ 120) (1);
1* - 705 (2)
Ca96
6.1(v)
1* - 300 (mostly
< 130)
Wi62
NR to RN
N to RN
Pinarbasi,
Erdogmus, Sazkoy,
Muratdag
1975 Oroville, USA
5.9
Cleveland Hill
1980 Irpinia, Italy
6.9
Irpinia
Notes
(1) Measured in paleoseismological trenches. (2) Measured at the surf ace.
(1) SR along the main range-f ront f aults. Three local FW splays 115-to-670 mlong, distant up to 50-135 m f rom MF (Pearce f ault). (2) Broad discontinuous
zone of SRs parallel to MF (Pearce f ault), 4.5 km-long, in the stepover zone
betw een Pearce and Sou Hills f aults (separation betw een f aults = 2.5-to-5
km).
WRZ is calculated f or the 5.5 km-long Llamacorral segment on a ~1:43,500
tectonic map and a ~1:3,700 map (Fig. 2 in Be91). Local FW splay, 145 mlong, distant up to 25-30 m f rom MF (central part of the segment).
Large WRZ (280-to-380 m) due to a 360 m-long (4.1% of SRL) antithetic HW
splay.
WRZ > 150 m f or 6.6 km (20.9% of SRL) along lef t-stepping and right-steping
bif urcations f rom MF at the "Bell Canyon salient" (major geometric complexity
of MF) and at the "US Highw ay 50" lef t-stepping and parallel segments; tw o
local FW splays 170-to-270 m long, distant up to 305 m f rom MF.
Tw o parallel ruptures, separated by 220-270 m, overlapping f or 395 m, at the
souther termination of the main rupture zone. It is unclear w hich one is the MF
(possible FW splay?). Probably, partial reactivation of the stepover zone
betw een tw o major lef t-stepping segments.
Discontinuous ruptures, mostly along lef t-stepping en echelon segments;
overlapping zones betw een adjacent segments (separation ranging f rom 140
to 195 m) are not considered in calculating WRZ; WRZ is calculated f or each
segment.
Discontinuous ruptures; overlapping zones betw een en echelon segments
(separation ranging f rom 305 to 625 m) are not considered in calculating
WRZ; WRZ is calculated f or each segment.
Discontinuous complex ruptures along right-stepping en echelon and/or
parallel segments; maximum WRZ (580 m) f or 1.4 km-long system of 3 parallel
segments (central part of SR zone).
(1) SR along the main range-f ront f ault: WRZ > 120 m only f or 2.28 km (5.4 %
of SRL) along lef t-stepping bif urcations f rom MF near "The Bend" (major
geometric complexity of MF; i.e.,relay zone betw een northern and southern
Dixie V. segments) and at the southern termination of the MF; tw o local FW
splays 285-to-320 m long, distant up to 140-260 m f rom MF near "The Bend".
(2) Broad discontinuous zone of SR on the piedmont of "The Bend" area (i.e.,
major geometric complexity of MF).
WRZ > 150 m f or 1.24 km (4.7% of SRL) along sharp bend betw een northern
and southern segments of the Red Canyon f ault (major geometric complexity
of MF); three local FW splays 440-to-800 m-long, distant 90-to-780 m f rom MF
(near the bend of Red Canyon f ault).
WRZ > 130 m in broad def ormation zones at lateral terminations of major f ault
segments (bif urcations f rom MF, systems of en echelon f ractures). One HW
splay, 175 m-long, distant 170-to-210 m f rom MF (Akcaalan segment). Local
FW splays, 170-to-190 m-long, distant 30-to-55 m f rom MF (Akcaalan
segment).
(1) Large WRZ (260-to-450 m) results f rom overlapping of tw o right-stepping
major f ault segments (a w estern segment, f ormed by the south and
northw est colinear breaks of Cl76, and an eastern segment, f ormed by the
northeast break of Cl76). (2) WRZ measured individually f or the tw o rightstepping segments. Local short f ootw all crack, ~60 m-long, distant ~30 m
f rom MF (south break).
Kinematics = normal or normal-oblique
Hebgen, Red
7.1
Main fault
%SRL HW, ≤150 %SRL HW, ≤40 %SRL FW
100
100
0
98.0 (calculated
for (1))
90.6
2.2
100
94.2
2.6
95.9
95.9
0
79.1
70.2
1.4
100
95.7
0(?)
100
98.4
0
100
100
0
56.4
53.6
0
95.6 (calculated
for (1))
92.9
1.4
95.3
91.3
6.5
98.4
89.9
1.3
35.5 (1); 100 (2)
35.5 (1); 100 (2)
1.6
NL to N
42
2.75(v) 0.8 (h)
1* - 285 (mostly
< 130)
Ta71
N to NR
3.8
0.55(v)
1* - 450 (1);
1* - 30 (2)
Cl76
N
30
1.3(v)
1* - 25
PV90
Measured in paleoseismological trenches.
100
100
0
100
not quantified
0
FW splay
N
12-15
1(v)
1* - 70
Pa93,
PC04
The Pisia and Shonos rupture zones occurred at or a f ew meters dow nslope
of the MF. Near the f oot of an alluvial f an the Shinos rupture zone divided in a
series of right-stepping en echelon f ractures w ith WRZ of ~70 m.
Lost River
N to NL
33.3
2.7(v) 1.0(h)
1* - 780 (mostly
≤ 140)
Cr87
WRZ > 140 at major geometric complexities of MF (e.g., 1.3 km-long West
Spring Block, southern section of MF, WRZ up to 780 m) and at a ~1.7 kmlong HW graben, partially reactivated in 1983, up to 240 m-w ide (northern
section, Gooseberry Creek). Local FW splay, 740 m-long, distant up to 120 m
f rom MF (southern section, site E of Cr87).
92.3
82.5
2.2
5.8
Kalamata
N
6
0.18(v)
1* - 60
Ly88
Detailed description laking; maximum WRZ obtained f rom 1:59,000 tectonic
map (Fig. 2b of Ly88).
100
~95
0
6.3
Edgecumbe, Onepu,
Rotoitipakau (preexisting) and Aw aiti,
Otakiri, Te Teko,
Omeheu (new )
N
21.7 (1);
16.3 (2)
2.5(v)
1* - 80
Be89
(1) obtained by summing the length of each individual f ault; (2) length of the
system along the average strike. WRZ exceeds 40 m only at 5 sites along the
Edgecumbe f ault.
100
not quantified
(>98)
0
6.6
Aliakmon River
N
30
0.18(v)
1* - 70
Ch98,
Mo98
WRZ f rom 1:4,000 map in Fig. 2 of Ch98 (only part of SRL); surf ace ruptures
coinciding w ith or very close to pre-existing MF scarps.
6.2
Egion
N
7.2
0.03(v)
1* - 60
KD96
En echelon ruptures at the w estern termination of MF; separation betw een
segments f rom 80 to 150 m.
100
FB06
WRZ f rom ~1:10,000 maps in Fig. 3 of FB06 (only part of SRL); (1) f ault is
draw n w ith dextral component on map, but is said lef t in the text and photo;
(2) maximum value in the northern strands.
100
1981 Corinth,
Greece
6.7
Pisia, Shinos
1983 Borah Peak,
USA
7.3
1986 Kalamata,
Greece
1995 West
Macedonia
1995 Egion,
Greece
1.0(v)
18 earthquakes
7.3 Canyon,
N
26.5
Width
of West
the Rupture
Zone
Yellowstone Basin
Akcaalan, (WRZ)
1970 Gediz, Turkey
1987 Edgecumbe,
New Zealand
59
MD (m)
7.2
Louderback Mts.
1954 Dixie Valley,
USA
N
36
2006 Machaze,
Mozambique
7.0
2009 L'Aquila, Italy
6.3
Borah Peak 1983 M 7.3
Crone et al., 1987 BSSA
Machaze
Paganica, San
NL (1)
>15 (3040)
2.05(v) 0.7(h)
1* - 140 (2)
N
13
0.12(v)
1* - 140
this paperMost constrained data along the Paganica f ault.
not quantified
100
not quantified
0
not quantified
98.7 (Paganica)
0
Data from world-wide normal faulting earthquakes
For simple fault traces, without major complexities:
• WRZ mostly ≤ 120-150 m;
• >95% of SRL with ruptures in the HW within 150 m from MF trace;
• >80-90% of SRL with ruptures in the HW within 40 m from MF trace;
• FW splays are not systematic features: absent or <1.5-2.5% of SRL.
Zoning Surface Fault-Rupture Hazard along normal faults
Boncio et al., 2012 BSSA
Verso un aggiornamento degli Indirizzi e Criteri per la Microzonazione Sismica
Roma, aprile 2013
Verso un aggiornamento degli Indirizzi e Criteri per la Microzonazione Sismica
Verso un aggiornamento degli Indirizzi e Criteri per la Microzonazione Sismica
Verso un aggiornamento degli Indirizzi e Criteri per la Microzonazione Sismica
Verso un aggiornamento degli Indirizzi e Criteri per la Microzonazione Sismica
Verso un aggiornamento degli Indirizzi e Criteri per la Microzonazione Sismica
Verso un aggiornamento degli Indirizzi e Criteri per la Microzonazione Sismica
Livello 1 di MS
NB: La ZAFAC rimanda obbligatoriamente al Livello 3
Verso un aggiornamento degli Indirizzi e Criteri per la Microzonazione Sismica
Livello 1 di MS
Verso un aggiornamento degli Indirizzi e Criteri per la Microzonazione Sismica
Livello 3 di MS
Verso un aggiornamento degli Indirizzi e Criteri per la Microzonazione Sismica
Livello 3 di MS
ZR e Zl possono essere asimmetriche:
Verso un aggiornamento degli Indirizzi e Criteri per la Microzonazione Sismica
Livello 3 di MS
Verso un aggiornamento degli Indirizzi e Criteri per la Microzonazione Sismica
Verso un aggiornamento degli Indirizzi e Criteri per la Microzonazione Sismica
... lastly
• Italy lacks of official maps of active/capable faults. Official maps are
required, for example, by the Eurocode 8 – Part 5 in order to build
regulatory zones around active faults.
Therefore, there is an urgent need of a national-scale OFFICIAL map of
active/capable faults.
!