σ3

σ1

σ3

σ1

σ

σ

σ

1

2

3

ItalyUpper PleistoceneTravertine

Middle PleistoceneVolcanics

Plio-QuaternarySedimentary Units

Meso-CenozoicCarbonatesVico

Lake

Bracciano

Lake

Albano

Lake

Sabatini

Vico

Colli Albani

Tiber River

Rome

Tyrrhenian Sea

0 20 km

Sabin

a F

ault

1996 Cecchignola earthquake (Ml=3.6)

P T

Stress field from geological and structural analysis on faults in blue

Stress field from geological and structural analysis on faults in blue

Stress field from earthquake focal mechanismsStress field from earthquake focal mechanisms

Inversion of focal mechanisms

(Aft

er

Marr

a,

1999)

AG 0.1

Roma

Capannelle

1989-1990

Seismicity

Albano

NW SE

Eleva

tion (m

)Depth

(Km

)

0

0

1010 20 300

100

200

300

400

500

1951-1994

Ariccia

VelletriCisterna

di Latina

Eleva

tion change (cm

)

30

20

10

0

Geometry of the Geodetic LinesUplift and Seismicity

Roma

Capannelle

Ariccia

crater

MT

CA INGVAlbano

Lake Rocca di

Papa

Nemi

Lake

Velletri

Caldera rim

Cisterna di

Latina

41°40'N

12°40'E0.0

0.0

0.3

Distance (Km)

0 5Km

1954-1994

1927-1994

1891, 1927,

1951, 1994

AG Ariccia-Galloro

LEGEND

MT Madonna del Tufo

CA Palazzo Cantarini

INGV Istituto Nazionale di

Geofisica e Vulcanologia

1994

1994

discarted

(Chiarabba et al., 1997)

(Salvi et al., 2004)

Legend

1.11 - 3.00

3.01 - 4.50

4.51 - 6.00

6.01 - 10.00

Seismic stations

Eq. depths

4620000

4630000

300000 310000 320000

s.l.Volcanic

units

Shales

Sandstone

Conglomerate

Ple

isto

cene

Low

er

Pliocene

Shales

0

100

200

300

400

500

600

700

800

Stratigraphic sketch

Initialconditions

Fracturing

Shut-in(fracture closure)

Reopening

Injection flow Qw Injection flow Qw

First pressurization Second pressurization

TIME

Well pressure Pw

Pw>Pb

Pw

Pw=PsPs=Shminσh

σHσθmin

σθmin=0

Pw>Pr

(Rutqvist et al., 2000)

Flowmeter

Wireline

High PressureHose

Fracture

Borehole

Packer

Transducer

Hydraulic Pump(packers)

Hydraulic Pump(test interval)

Data AcquisitionUnit

Pressure

ROME

Alban Hills T=33°C

T=40°C

selected location

crustaldeep

strike-slipcompressive

extensive

Rome

SEISMICITY

45N

10E 15E

40NTyrrhenian Sea

Adriatic Sea

Ionian Sea

Po Plain

Tuscany

Sicily

Friuli

Molise

0

100

200

400

800

1500

2500

5000

meters a.s.l.

km0 50 100

Projection: Lambert Azimuthal Equal Area

40˚N

44˚N

12˚E

16˚E

Tyrrhenian Sea

Adriatic Sea

Ionian Sea

Sicily

Cala

bria

Alps

Friuli

Po Plain

Rome

Tuscany

Northern Apennines

Southern Apennines

Dataset (364 data)

Formal inversions:20 σ3 directionsB quality: 19C quality: 1

Well data courtesy of Eni-Agip,Enel and Enterprise Oil

Fault data:7 C quality data

Borehole breakouts:150 Shmin directionsA quality: 10B quality: 65C quality: 75 (1 from WSM)

Focal plane solutions:186 Shmin directionsB quality: 99C quality: 87

155 CMT solutions (1976-2003)4.0<Mw<7.0hypocentral depths: 5-37 km

31 polarity solutions (1908-1995)4.0<M<7.0hypocentral depths: 0-38 km

Shmin direction Data quality

breakout data

earthquake data

fault data

Stress regimenormal faulting: Sv>SHmax>Shmin

thrust faulting: SHmax>Shmin>Sv

strike-slip faulting: SHmax>Sv>Shmin

stress regime unknown

A

B

C

Overcoring1 C quality data (from WSM)

overcoring

Sardinia

(Montone et al., 2004)

M.Teresa Mariucci, Paola Montone, Simona Pierdominici

Drilling a Volcano: Scientific Experiment at Alban Hills, Italy

1

2

3

4

V21D-0643mariucci@ingv.it

Str

ess m

ap

of

Ita

ly

Seis

mic

ity a

nd

fo

cal

mech

an

ism

s

Abstract

Istituto Nazionale diGeofisica e Vulcanologia

Via di Vigna Murata 605

00143 Roma IT

Only a few deep boreholes have been drilled for scientific purposes on active volcanoes in the whole world. Indeed, data collected from deep

wells are fundamental to better model geophysical processes. Within the Italian research project INGV-DPC-V3.1 (funded by the Italian Civil

Protection Department), we planned to drill a 400m hole with the main goal to define the orientation and magnitude of present stress

field in the shallow crust in the Alban Hills. The Alban Hills are considered a quiescent volcanic district, belonging to the Quaternary volcanic

belt of the Tyrrhenian coast. They are located in a densely populated area close to Rome, then an eruption would be a real risk, also

considering the type of their past activity. Alban Hills have been fully studied by means of surface or very shallow observations and indirect

methods: now we are going to start the first scientific program to investigate them directly at depth. We will perform some hydrofracturing

tests at different depth in the drilling located in a key area, to compute, for the first time beneath a volcano, the absolute values of stress

principal axes and reconstruct the stress path along depth. Analysis on core samples will allow to better understand the geomechanical

characters of volcanic rocks and their underlying sedimentary basement. Coupling these studies with structural, geochronological and

palaeomagnetic investigations will constrain the recent volcano-tectonic processes. The comparison of new data with the available stratigraphic

logs will give insights on the occurrence of tectonic movements. Analysis of the anisotropy of the magnetic susceptibility could provide

information on the Middle Pleistocene strain to be compared with present-day data. These results, will be integrated with new geodetic and

seismological data obtained by other research units and will be used for physical and numerical modeling to understand the behavior of the

whole volcanic complex. This experiment represents a first step to test methods and instruments for future applications also in other sites. At

the end of the project, the borehole will be used to host instruments, e.g. a seismometer that will provide good quality seismic data in such a

noisy area where earthquakes are characterized by swarms of small magnitude and shallow depth.

Brief description of the project

Introduction to the area

Research Unit

What we are going to do

At the end ........ a seismometer at depth!

Further steps......

M.Teresa Mariucci (INGV- RM1 Dpt.)

Paola Montone (INGV- RM1 Dpt.)

Simona Pierdominici (INGV- RM1 Dpt.)

Fabrizio Marra (INGV- RM1 Dpt.)

Fabio Florindo (INGV- RM2 Dpt.)

Hydraulic Fracturing Test (or extended leak-off tests) to determine active

stress orientation and magnitude

Downhole LoggingFour-arm Dipmeter

Borehole Televiewer

Sonic log

Gamma Ray log

Magnetic log

Electric log

Comparison with new geodetic, seismic and geological-structural data

Laboratory tests on cores (i.e. Vp-Vs measurements)

Gas and fluid sampling in the borehole

Some researchers from INGV (CNT Dpt.) will install a broad-band

seismometer at 200-300m that will be connected in real-time with the

Italian Seismic Network and provide low noise recordings in a densely

populated area and where few seismic stations are present.

INGV - Seismology and Tectonophysics Department - Rome (Italy)

This project is partially funded by the Italian "Dipartimento della Protezione

Civile" (DPC) in the frame of the 2004-2006 Agreement with "Istituto Nazionale

di Geofisica e Vulcanologia" (INGV). It is part of the PROJECT DPC-INGV V3.1.

Within the TASK 4 "Structure and Dynamics of the Volcanic District" our

research unit would like to define the orientation and intensity of the

present stress field and its evolution in recent time.

Project DPC-INGV V3.1 "Colli Albani"Coordinators: P. Scarlato (INGV-RM1) and M. Gaeta (Univ. Roma)

This project is part of the Project V3 "Research on active volcanoes, precursors, scenarios, hazard,

and risk", Responsibles: P. Papale, (INGV-RM1) and S. Gresta (Univ. Catania).

The Alban Hills Volcanic District has been identified as a quiescent volcano only recently and the

present project is the first one specifically oriented to the definition of their potential hazard and crisis

levels. Main topics:

1) Evolution and present-day state of the magmatic system, including the presence and location of

possible magma chambers and the role on magmatic processes on the origin of surface gas output.

2) Genesis and mobility of hazardous gases in ground and surface water bodies, degassing cycles and

effects on degassing of anthropic hydrological perturbations.

3) Deep setting of the District and the source of seismicity and regional-scale ground deformation.

4) Dynamics of the District at shallow and surface depth and their interferences with human activities,

including local-scale ground deformation, stress field, slope stability, recent eruptive processes, crater

lake evolution, quaternary mass flows.

Str

ess f

ield

We propose to perform some Hydrofrac tests (or Leak-off) in a 400m borehole to compute the values of

stress principal axes. The borehole will allow to characterise the geomechanical behaviour of drilled rocks

and to couple these studies with geochronology and palaeomagnetic investigations to constraining the

recent volcano-tectonic processes.

ReferencesChiarabba C., A. Amato, P. T. Delaney (1997), Bull. Volcanol., 59, 161-170.

Cornet F.H., M.L. Doan, F. Fontbonne (2003), Int. J. Rock Mech. Min. Sci., 40, 1225-1241.

Haimson B.C. and F.H. Cornet (2003), Int. J. Rock Mech. Min. Sci., 40, 1011-1020.

Haimson B.C., M.Y. Lee, I. Song (2003), Int. J. Rock Mech. Min. Sci., 40, 1243-1256.

Klee G., F. Rummel, A. Williams (1999), Int. J. Rock Mech. Min. Sci., 36, 731-741.

Marra F. (1999), Geophys. J. Int., 138, 231-243.

Montone P., M. T. Mariucci, S. Pondrelli, A. Amato (2004), JGR, 109, doi:10.1029/2003JB002703.

Reinecker J., O. Heidbach, M. Tingay, P. Connolly, B. Müller (2004), available online at www.world-stress-map.org

Rutqvist J. and O. Stephansson (1996), Int. J. Rock Mech. Min. Sci., 33, 7, 695-711.

Salvi S., S. Atzori, C. Tolomei, J. Allievi, A. Ferretti, F. Rocca, C. Prati, S. Stramondo, N. Feuillet (2004), GRL, 31, doi:10.1029/2004GL020253.

Zoback M.D., C.A. Barton, M. Brudy, D.A. Castillo, T. Finkbeiner, B.R. Grollimund, D.B. Moos, P. Peska., C.D. Ward, D.J. Wiprut (2003), Int. J. Rock Mech. Min. Sci., 40, 1049-1076.

Magnetostratigrafy of the sedimentary units

Anisotropy of the Magnetic Susceptibility to provide information on the Middle Pleistocene strain to be

compared with present-day data

40Ar/39Ar dating of unknown pyroclastic horizons possibly recovered

Occurrence of seismic swarms

Only one stress data in the Alban Hills and none stress magnitude

Local tectonics different from regional one

The uplifted area coincides with the zone of recent seismicity

1989-1990 seismic swarm

(Haimson et al., 2003)

Sv = lithostatic load

Sh = from HF or LOT

SH = 3Sh - 2 Po

Po = pore pressure