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Today's earthquake in central Italy, initial report

For a quick jump directly to a map of affected populations, go here



NEIC Event Executive Summary
Mw 6.3 Central Italy
April 06, 2009, 01:32:42 UTC (03:32:42 Local Time = UTC + 2hr)
Version 1

42.423N 13.395E, Depth 10km (6.2 miles)
Location Last Updated at 04/05/2009 20:31:23 (Mountain Time)
Event Coordinator: Sipkin, Stuart A.(sipkin@usgs.gov)

Nearest Cities
70 km (40 miles) W of Pescara, Italy
95 km (60 miles) NE of ROME, Italy
115 km (70 miles) SE of Perugia, Italy
135 km (85 miles) S of Ancona, Italy

Tectonic Summary
The April 6th 2009 earthquake in Central Italy occurred as a result of normal faulting on a NE-SW oriented structure in the central Apennines, a mountain belt that runs from the Gulf of Taranto in the south to the southern edge of the Po basin in northern Italy. Geologically, the Apennines are largely an accretionary wedge formed as a consequence of subduction. This region is tectonically and geologically complex, involving both subduction of the Adria micro-plate beneath the Apennines from east to west, continental collision between the Eurasia and Africa plates building the Alpine mountain belt further to the north and the opening of the Tyrrhenian basin to the west. The evolution of this system has caused the expression of all different tectonic styles acting at the same time in a broad region surrounding Italy and the central Mediterranean. The April 6th, 2009 earthquake is related to normal faulting and the east-west extensional tectonics that dominate along the entire Apennine belt, primarily a response to the Tyrrhenian basin opening faster than the compression between the Eurasian and African plates.

The central Apennine region has experienced several significant earthquakes in recorded history. In 1997, a significant Mw 6.0 earthquake, located 85 km north-northwest of today's quake, killed 11, injured over 100 and destroyed approximately 80,000 homes in the Marche and Umbria regions. The 1997 event was part of a series of earthquakes known as the Umbria-Marche seismic sequence, which included eight events of magnitude greater than M 5.0 in a two-month period between September and November of 1997.

Talking Points
Located in the active seismic zone running down the spine of central Italy
Preceded by M4.0 and M3.5 foreshocks by approximately 5 hr and 3 hr, respectively
Largest recent event was M6.0 on 26 September 1997

Historical Seismicity
1997 09 26, 09 40 26.3, 43.084 N 12.812 E 10
CENTRAL ITALY. Mw 6.0 (GS), 6.0 (HRV)

Located 85 km to the north-northwest of today's event.

Eleven people killed, more than 100 injured and about 80,000 homes destroyed or damaged in the Marche and Umbria regions by this earthquake and the event at 00:33:12 UTC on September 26. Maximum intensity (X) at Serravalle di Chienti and (IX) at Valtopina. Extensive damage to the Basilica of St. Francis at Assisi. Felt in many parts of central and northern Italy from Bologna and Modena to Rome. Felt (IV) in western and central Slovenia and (III) in southern Karnten Province, Austria.

Today's Aftershocks
M 4.8 2009/04/06 02:37:06

Style of Faulting: Normal (a NW striking fault with down to the SW)

Body Wave Moment Tensor
09/04/06 01:32:42.76
CENTRAL ITALY
Epicenter: 42.411 13.348
MW 6.2

USGS MOMENT TENSOR SOLUTION
Depth 2 No. of sta: 99
Moment Tensor; Scale 10**18 Nm
Mrr=-2.34 Mtt= 0.92
Mpp= 1.42 Mrt=-1.72
Mrp=-0.60 Mtp=-0.81
Principal axes:
T Val= 2.12 Plg=10 Azm=222
N 1.12 23 128
P -3.25 63 335

Best Double Couple:Mo=2.8*10**18
NP1:Strike=113 Dip=60 Slip=-118
NP2: 340 40 -51

#######
-------##########
------------#########
----------------#########
--------------------#########
----------------------#########
#----------- --------########
###---------- P ---------########
####--------- ----------#######
######--------------------#######
########------------------#######
###########----------------######
##############------------#####
#####################----###---
### ##################-----
# T #################----
################---
###############--
#######

Regional Moment tensor
09/04/06 01:32:44
CENTRAL ITALY
Epicenter: 42.480 13.160
MW 6.2

USGS/SLU REGIONAL MOMENT TENSOR
Depth 8 No. of sta: 20
Moment Tensor; Scale 10**18 Nm
Mrr=-2.31 Mtt= 0.76
Mpp= 1.55 Mrt=-0.23
Mrp= 0.33 Mtp=-1.08
Principal axes:
T Val= 2.34 Plg= 4 Azm=235
N 0.01 0 145
P -2.35 85 54

Best Double Couple:Mo=2.3*10**18
NP1:Strike=145 Dip=50 Slip= -90
NP2: 325 40 -90

#######
#################
#--------############
##------------###########
####---------------##########
#####-----------------#########
#####------------------########
#######------------------########
#######--------- -------#######
########-------- P --------######
#########------- --------######
##########------------------#####
##########-----------------####
# ########---------------####
T ##########-------------###
############----------##
###############------
#################
#######

W Phase Moment tensor
09/04/06 1:32:42
CENTRAL ITALY
Epicenter: 42.423 13.394
MW 6.2

USGS/WPHASE CENTROID MOMENT TENSOR
09/04/06 01:32:42.00
Centroid: 42.423 13.395
Depth 15 No. of sta: 38
Moment Tensor; Scale 10**16 Nm
Mrr=-2.57 Mtt= 1.01
Mpp= 1.56 Mrt=-0.74
Mrp=-1.24 Mtp=-1.24
Principal axes:
T Val= 2.61 Plg= 6 Azm= 54
N 0.57 22 147
P -3.19 66 309

Best Double Couple:Mo=2.9*10**18
NP1:Strike=121 Dip=43 Slip=-122
NP2: 343 55 -61

#######
------###########
----------###########
--------------##########
-----------------######### T
#------------------######## #
#---------- ------###########
###--------- P -------###########
####-------- --------##########
####-------------------##########
######------------------#########
#######-----------------#########
########---------------########
###########------------########
#############---------######-
###################------
#################----
##############---
#######

PAGER Population Exposure
(Modified Mercalli Intensity scale and number of people reporting)
MMI VIII: 68K ---- Severe Shaking
MMI VII: 28K
MMI VI: 34K
MMI V: 1,323K ---- Moderate Shaking
USGS Event Link
http://earthquake.usgs.gov/eqcenter/recenteqsww/Quakes/us2009fcaf.php
Prompt Assessment of Earthquakes for Response
http://earthquake.usgs.gov/eqcenter/pager/events/us/2009fcaf/index.html

If there are any changes, suggestions, questions, or comments about this particular email, please contact benz@usgs.gov
Tags: science
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