VZCZCXRO0831
RR RUEHDU RUEHJO RUEHMR RUEHRN
DE RUEHTO #1032/01 2271353
ZNR UUUUU ZZH
R 151353Z AUG 06
FM AMEMBASSY MAPUTO
TO RUEHC/SECSTATE WASHDC 5861
INFO RUCNSAD/SOUTHERN AFRICAN DEVELOPMENT COMMUNITY
RUEHAN/AMEMBASSY ANTANANARIVO 0029

UNCLAS SECTION 01 OF 03 MAPUTO 001032 
 
SIPDIS 
 
SIPDIS 
 
USAID/DCHA/OFDA FOR GMAYBERRY 
USAID FOR AA/AFR AND AFR/SA 
 
E.O. 12958: N/A 
TAGS: EAID PHUM MZ
SUBJECT: Mozambique: USGS and USAID/OFDA Assessment of 
February 23 Earthquake 
 
Ref: Maputo 232 
 
Maputo 241 
 
¶1. Summary.  A magnitude (M) 7.0 earthquake that occurred in 
Machaze, Mozambique on February 23, 2006 raised awareness 
that a large earthquake could occur in the country. 
Detailed analysis of the seismicity in Mozambique is needed 
to determine if a large earthquake could occur near highly 
populated areas or significant infrastructure such as the 
Cahora Bassa dam.  The first step in assessing the potential 
seismic risk in the country is to strengthen the national 
seismic network in order to pinpoint the location of small 
earthquakes, which reveal the location of faults that have 
the potential for larger earthquakes in the future.  A team 
composed of the USAID Office of U.S. Foreign Disaster 
Assistance (USAID/OFDA) geoscience advisor and seismologists 
from the U.S. Geological Survey (USGS) visited the area of 
the earthquake and met with key members of the local 
geological community to determine what is needed to 
strengthen the Mozambique seismic network.  They determined 
that the highest priority was for upgrading existing seismic 
stations, adding seismic monitoring equipment, and training 
Direccao Nacional de Geologia (DNG) staff.  End summary. 
 
-------- 
Overview 
-------- 
 
¶2. A large earthquake occurred in Machaze, Mozambique on 
February 23 at 1219 am local time (ref A).  According to the 
USGS National Earthquake Information Center (NEIC), the 
earthquake had a magnitude (M) of 7.  Although this was a 
large-magnitude earthquake, there was little loss of life 
and little damage because the earthquake occurred in an area 
with low population density where homes are constructed of 
light-weight, flexible materials.  If an earthquake of this 
size occurred in a highly populated region in Mozambique, 
for instance the cities of Beira or Maputo, the impact could 
be much greater.  The seismic network in Mozambique, which 
is used to record and locate earthquakes, is inadequate by 
modern standards.  It consists of only four stations, three 
of which are equipped with obsolete seismographs and have no 
telecommunications capability.  Accordingly, the seismic 
hazard in the country is not well known because the network 
cannot locate small earthquakes, which are indicative of 
where larger ones could occur. 
 
¶3. In response to the M 7 earthquake, seismologists from the 
USGS, with funding from USAID/OFDA, traveled to Mozambique 
to work with the DNG.  They evaluated the potential for 
large (M greater than 6) earthquakes that could pose a 
threat to populated regions or to critical infrastructure 
including the Cahora Bassa concrete arch dam on the Zambezi 
river.  The seismologists found that in-kind support and 
funding that DNG had received from other donors met some of 
their needs, but there is still a need to 1) upgrade 
existing seismic stations, 2) add new stations for better 
coverage, and 3) train the staff to operate and maintain the 
new systems as well as to analyze complex seismic data. 
 
¶4.  In order to help DNG assess the seismic hazard in 
Mozambique, which will help the government and at-risk 
communities prepare for large earthquakes, USGS proposes to 
cooperate with DNG for a major upgrade of the Mozambique 
seismic network.  This proposed project will involve 
establishing four new stations and upgrading three current 
stations so that broad-band, real time data are available. 
The future upgraded Mozambique seismic network would consist 
of several broad-band stations communicating data in real 
time to the DNG headquarters.  USGS proposes to provide 
technical assistance in site selection, training, and 
evaluation of performance.  The primary goal of this 
proposed effort is to assist the DNG staff in developing an 
independent and self-sufficient Seismic-Hazard Reduction 
Center in Mozambique that collects and processes regional 
seismic data in real time and interprets these data in ways 
useful to the mitigation of earthquake effects. 
 
¶5.  With funding from USAID/OFDA, during July 17 through 20 
two USGS seismologists and the USAID/OFDA geoscience advisor 
travelled to Mozambique.  Their goal was to determine what 
assistance DNG needs in order to improve their seismic 
network so they can eventually issue real time earthquake 
notifications and produce a detailed map of the seismic 
hazard in the country.  The group also evaluated the 
potential for large (M greater than 6) earthquakes to pose a 
threat to highly populated areas and critical facilities. 
While in-country they met with staff from the U.S. embassy 
 
MAPUTO 00001032  002 OF 003 
 
 
in Maputo, the USAID mission, Direccao Nacional de Geologia, 
and the administrator of Chitobe near where the earthquake 
occurred.  In South Africa, the team met with the Resources 
and Science Specialist with the U.S. Consulate in 
Johannesburg, the USAID/OFDA Regional Advisor for southern 
Africa, and representatives from the USAID office of Food 
For Peace, the U.S. Agency for International Development 
(USAID), and the UN Office for the Coordination of 
Humanitarian Affairs (OCHA). 
 
¶6.  The trip to Mozambique was preceeded by a visit to the 
Africa Array workshop in Johannesburg, South Africa, during 
July 20 through 21.  Attending the workshop allowed the 
assessment group to meet with the director of DNG, current 
and potential donors to the Mozambique seismic network, and 
members of the seismological community from other African 
countries who would be able to share seismic data with 
Mozambique, futher strengthening their network. 
 
---------------- 
Geologic setting 
---------------- 
 
¶7.  The NEIC reported that the February 23rd earthquake 
occurred near the southern end of the East African rift 
system.  The East African rift system is a diffuse zone of 
crustal extension that passes through eastern Africa from 
Djibouti and Eritrea on the north to Malawi and Mozambique 
on the south.  The East African rift results from spreading 
between the Africa tectonic plate on the west and the 
Somalia plate on the east.  At the earthquake's latitude, 
the Africa and Somalia plates are spreading apart at a rate 
of several millimeters per year.  The largest earthquake to 
have occurred in the rift system since 1900 had a magnitude 
of about 7.6.  The western branch of this rift terminates in 
southern Mozambique, while the eastern branch travels 
through Kenya and continues into Tanzania.  There is 
persistent seismicity within the Mozambique channel, 
suggesting that the eastern branch of the rift may continue 
into the Indian Ocean, possibly to the southwestern Indian 
Ocean ridge. 
 
------------ 
Field survey 
------------ 
 
¶8.  The M 7 earthquake on February 23rd occurred in Machaze, 
the southernmost district in the western province of Manica, 
about 215 km (135 miles) SW of the city of Beira, 
Mozambique.  There were reports of 4 deaths, 36 injuries, 
and 1,440 people made homeless.  The earthquake was felt as 
intensity VI (strong perceived shaking, light potential 
damage) in Beira, approximately 215 km (135 miles) northeast 
of the location of the earthquake, and intensity IV (light 
perceived shaking, no potential damage) in Maputo, about 500 
km (310 miles) to the south.  Within the epicentral area 
(the area near where the earthquake occurred), spectacular 
surface faulting was seen, with a crack actually running 
through a traditionally built dwelling and one splitting a 
tree.  Extensive liquefaction was also seen, which is a 
process by which water-saturated sediment temporarily loses 
strength and acts as a fluid.  The maximum surface slip of 
about 2 meters was consistent with the large magnitude 
measured for this earthquake. 
 
¶9.  The primary natural hazard affecting Mozambique is 
flooding, a result of low-lying topography and heavy 
rainfall.  Earthquakes, in contrast, are thought to be a 
much less important source of hazard, largely because the 
African continent generally has quite a low level of natural 
seismicity.  Similarly, the February 23rd Machaze 
earthquake, although of considerable magnitude, resulted in 
few casualties and severe damage to only a small number of 
dwellings considering the size of this earthquake for 
several reasons.  First, the epicentral region is sparsely 
populated.  Second, houses in the epicentral area were 
largely undamaged because most of these structures are made 
of light-weight materials as was reported by seismologists 
from Imperial College, England, who conducted a field survey 
shortly after the earthquake.  In contrast, many of the 
structures made of unreinforced brick masonry collapsed to 
some extent, resulting in a few fatalities.  Third, 
earthquakes with associated surface faulting tend to yield 
lower levels of damaging ground motion compared to those 
involving buried faults (no surface rupture).  Fourth, 
earthquakes in extensional tectonic environments, including 
the East African rift belts where the Machaze earthquake 
occurred, show lower levels of damaging ground motion 
 
MAPUTO 00001032  003 OF 003 
 
 
compared to their counterparts in compressional environments 
(e.g. Iran). 
 
¶10.  To date, relatively little attention has been paid to 
the potential for seismic hazards in Mozambique, which is 
evidenced by the archaic and sparse seismic monitoring 
system currently in place in the country.  However, the 
nature and magnitude of the February 23rd Machaze earthquake 
has raised serious questions regarding the hazard associated 
with large earthquakes that might occur in densely-populated 
regions in Mozambique, or near critical facilities like the 
Cahora Bassa concrete arch dam on the Zambezi river.  The 
Cahora Bassa dam, the 2nd largest in Africa and the 4th 
largest in the world, has impounded an enormous reservoir 
and generates 2.1 mega-watts of electricity.  In the event 
of a nearby strong earthquake, the integrity of the dam 
might be compromised, resulting perhaps in flooding and loss 
of electrical power delivered to Mozambique, South Africa, 
and other neighboring countries. 
 
¶11.  Current seismic hazard maps of Mozambique lack detail 
and are based largely on expected seismicity associated with 
the East African rift.  However, it is possible that other 
types of faulting could be present, but are not yet 
identified from Mozambique's limited earthquake data base. 
Such additional sources of seismicity could change the 
hazard map to some extent.  Currently the seismic network 
run by DNG is too sparse to record and locate earthquakes at 
a sufficiently low magnitude threshold to determine the 
likely sources of damaging ground motion due to future 
earthquakes.  Currently, data from three of the four 
existing seismic stations that DNG runs are periodically 
retrieved manually and sent to the Council for Geosciences 
in South Africa for analysis, the results of which are then 
sent to DNG.  This process, which takes at least a month, 
precludes the possibility of responding to major damaging 
earthquakes in a timely manner, and also compromises the 
ability of the DNG to develop a realistic seismic hazard map 
based on up-to-date information. 
 
----------- 
Future plan 
----------- 
 
¶12.  The French embassy in Mozambique and the Council for 
Geoscience in South Africa have already provided DNG with 
computer equipment and training, respectively. Additionally, 
the Intergovernmental Oceanographic Commission (IOC) intends 
to establish three stations along the coast of Mozambique as 
part of the Indian Ocean tsunami warning network.  Based on 
the results from the assessment trip and pending funding, 
USGS proposes to work with DNG at their request to develop a 
new, vastly-upgraded Mozambique seismic network that will 
consist of eight stations equipped with state-of-the-art 
seismometers, digitizers, and telemetry via cellular 
technology. 
 
¶13.  There are four key roles that the USGS plans to play: 
(1) definition of network goals and derived products, 
including seismic hazard maps, (2) assistance during network 
construction and evaluation of performance, (3) equipment 
acquisition and installation, and (4) training in network 
operations and data processing, ensuring that local 
scientists and engineers become independent operators of the 
network.  The primary end-product of this network will be 
the production of an improved probabilistic seismic hazard 
map for Mozambique.  This map will delineate the zones where 
the likelihood of damaging ground motion is the greatest so 
that appropriate hazard mitigation activities can be 
prioritized and undertaken.  Additionally, USGS will advise 
DNG in the development of information products to help 
educate the public about how to prepare for large 
earthquakes and tsunamis. 
 
¶14. This report was written by members of the USGS and 
USAID/OFDA team that visited Mozambique in July. 
 
 
Dudley