TSUNAMI
THREAT FOR AUSTRALIA AFTER M7.2 EARTHQUAKE
29 March, 2018
The Pacific Tsunami Warning Center is declaring a TSUNAMI THREAT for Northern Australia and Papua New Guinea (PNG) after a strong Magnitude 7.2 earthquake struck in the ocean off the coast of PNG.
ZCZC
WEPA40 PHEB 292157
TSUPAC
TSUNAMI MESSAGE NUMBER 2
NWS PACIFIC TSUNAMI WARNING CENTER EWA BEACH HI
2157 UTC THU MAR 29 2018
...PTWC TSUNAMI THREAT MESSAGE...
**** NOTICE **** NOTICE **** NOTICE **** NOTICE **** NOTICE *****
THIS MESSAGE IS ISSUED FOR INFORMATION ONLY IN SUPPORT OF THE
UNESCO/IOC PACIFIC TSUNAMI WARNING AND MITIGATION SYSTEM AND IS
MEANT FOR NATIONAL AUTHORITIES IN EACH COUNTRY OF THAT SYSTEM.
NATIONAL AUTHORITIES WILL DETERMINE THE APPROPRIATE LEVEL OF
ALERT FOR EACH COUNTRY AND MAY ISSUE ADDITIONAL OR MORE REFINED
INFORMATION.
**** NOTICE **** NOTICE **** NOTICE **** NOTICE **** NOTICE *****
THE TSUNAMI FORECAST IS UPDATED IN THIS MESSAGE.
PRELIMINARY EARTHQUAKE PARAMETERS
---------------------------------
* MAGNITUDE 7.2
* ORIGIN TIME 2126 UTC MAR 29 2018
* COORDINATES 5.6 SOUTH 151.6 EAST
* DEPTH 10 KM / 6 MILES
* LOCATION NEW BRITAIN REGION PAPUA NEW GUINEA
EVALUATION
----------
* AN EARTHQUAKE WITH A PRELIMINARY MAGNITUDE OF 7.2 OCCURRED IN
THE NEW BRITAIN REGION, PAPUA NEW GUINEA AT 2126 UTC ON
THURSDAY MARCH 29 2018.
* BASED ON ALL AVAILABLE DATA... HAZARDOUS TSUNAMI WAVES ARE
FORECAST FOR SOME COASTS.
TSUNAMI THREAT FORECAST...UPDATED
---------------------------------
* TSUNAMI WAVES REACHING 0.3 TO 1 METERS ABOVE THE TIDE LEVEL
ARE POSSIBLE FOR SOME COASTS OF
PAPUA NEW GUINEA.
* TSUNAMI WAVES ARE FORECAST TO BE LESS THAN 0.3 METERS ABOVE
THE TIDE LEVEL FOR THE COASTS OF
SOLOMON ISLANDS.
* ACTUAL AMPLITUDES AT THE COAST MAY VARY FROM FORECAST
AMPLITUDES DUE TO UNCERTAINTIES IN THE FORECAST AND LOCAL
FEATURES. IN PARTICULAR MAXIMUM TSUNAMI AMPLITUDES ON ATOLLS
AND AT LOCATIONS WITH FRINGING OR BARRIER REEFS WILL LIKELY
BE MUCH SMALLER THAN THE FORECAST INDICATES.
* FOR OTHER AREAS COVERED BY THIS PRODUCT A FORECAST HAS NOT
YET BEEN COMPUTED. THE FORECAST WILL BE EXPANDED IF
NECESSARY IN SUBSEQUENT PRODUCTS.
RECOMMENDED ACTIONS
-------------------
* GOVERNMENT AGENCIES RESPONSIBLE FOR THREATENED COASTAL AREAS
SHOULD TAKE ACTION TO INFORM AND INSTRUCT ANY COASTAL
POPULATIONS AT RISK IN ACCORDANCE WITH THEIR OWN
EVALUATION... PROCEDURES AND THE LEVEL OF THREAT.
* PERSONS LOCATED IN THREATENED COASTAL AREAS SHOULD STAY ALERT
FOR INFORMATION AND FOLLOW INSTRUCTIONS FROM NATIONAL AND
LOCAL AUTHORITIES.
ESTIMATED TIMES OF ARRIVAL
--------------------------
* ESTIMATED TIMES OF ARRIVAL -ETA- OF THE INITIAL TSUNAMI WAVE
FOR PLACES WITHIN THREATENED REGIONS ARE GIVEN BELOW. ACTUAL
ARRIVAL TIMES MAY DIFFER AND THE INITIAL WAVE MAY NOT BE THE
LARGEST. A TSUNAMI IS A SERIES OF WAVES AND THE TIME BETWEEN
WAVES CAN BE FIVE MINUTES TO ONE HOUR.
LOCATION REGION COORDINATES ETA(UTC)
------------------------------------------------------------
RABAUL PAPUA NEW GUINEA 4.2S 152.3E 2152 03/29
POTENTIAL IMPACTS
-----------------
* A TSUNAMI IS A SERIES OF WAVES. THE TIME BETWEEN WAVE CRESTS
CAN VARY FROM 5 MINUTES TO AN HOUR. THE HAZARD MAY PERSIST
FOR MANY HOURS OR LONGER AFTER THE INITIAL WAVE.
* IMPACTS CAN VARY SIGNIFICANTLY FROM ONE SECTION OF COAST TO
THE NEXT DUE TO LOCAL BATHYMETRY AND THE SHAPE AND ELEVATION
OF THE SHORELINE.
* IMPACTS CAN ALSO VARY DEPENDING UPON THE STATE OF THE TIDE AT
THE TIME OF THE MAXIMUM TSUNAMI WAVES.
* PERSONS CAUGHT IN THE WATER OF A TSUNAMI MAY DROWN... BE
CRUSHED BY DEBRIS IN THE WATER... OR BE SWEPT OUT TO SEA.
NEXT UPDATE AND ADDITIONAL INFORMATION
--------------------------------------
* THE NEXT MESSAGE WILL BE ISSUED IN ONE HOUR... OR SOONER IF
THE SITUATION WARRANTS.
* AUTHORITATIVE INFORMATION ABOUT THE EARTHQUAKE FROM THE U.S.
GEOLOGICAL SURVEY CAN BE FOUND ON THE INTERNET AT
EARTHQUAKE.USGS.GOV/EARTHQUAKES -ALL LOWER CASE-.
* FURTHER INFORMATION ABOUT THIS EVENT MAY BE FOUND AT
PTWC.WEATHER.GOV AND AT WWW.TSUNAMI.GOV.
* COASTAL REGIONS OF HAWAII... AMERICAN SAMOA... GUAM... AND
CNMI SHOULD REFER TO PACIFIC TSUNAMI WARNING CENTER MESSAGES
SPECIFICALLY FOR THOSE PLACES THAT CAN BE FOUND AT
PTWC.WEATHER.GOV.
* COASTAL REGIONS OF CALIFORNIA... OREGON... WASHINGTON...
BRITISH COLUMBIA AND ALASKA SHOULD ONLY REFER TO U.S.
NATIONAL TSUNAMI WARNING CENTER MESSAGES THAT CAN BE FOUND
AT NTWC.ARH.NOAA.GOV.
$$
NNNN
Seismotectonics of the New Guinea Region and Vicinity
The
Australia-Pacific plate boundary is over 4000 km long on the northern
margin, from the Sunda (Java) trench in the west to the Solomon
Islands in the east. The eastern section is over 2300 km long,
extending west from northeast of the Australian continent and the
Coral Sea until it intersects the east coast of Papua New Guinea. The
boundary is dominated by the general northward subduction of the
Australia plate.
Along
the South Solomon trench, the Australia plate converges with the
Pacific plate at a rate of approximately 95 mm/yr towards the
east-northeast. Seismicity along the trench is dominantly related to
subduction tectonics and large earthquakes are common: there have
been 13 M7.5+ earthquakes recorded since 1900. On April 1, 2007, a
M8.1 interplate megathrust earthquake occurred at the western end of
the trench, generating a tsunami and killing at least 40 people. This
was the third M8.1 megathrust event associated with this subduction
zone in the past century; the other two occurred in 1939 and 1977.
Further
east at the New Britain trench, the relative motions of several
microplates surrounding the Australia-Pacific boundary, including
north-south oriented seafloor spreading in the Woodlark Basin south
of the Solomon Islands, maintain the general northward subduction of
Australia-affiliated lithosphere beneath Pacific-affiliated
lithosphere. Most of the large and great earthquakes east of New
Guinea are related to this subduction; such earthquakes are
particularly concentrated at the cusp of the trench south of New
Ireland. 33 M7.5+ earthquakes have been recorded since 1900,
including three shallow thrust fault M8.1 events in 1906, 1919, and
2007.
The
western end of the Australia-Pacific plate boundary is perhaps the
most complex portion of this boundary, extending 2000 km from
Indonesia and the Banda Sea to eastern New Guinea. The boundary is
dominantly convergent along an arc-continent collision segment
spanning the width of New Guinea, but the regions near the edges of
the impinging Australia continental margin also include relatively
short segments of extensional, strike-slip and convergent
deformation. The dominant convergence is accommodated by shortening
and uplift across a 250-350 km-wide band of northern New Guinea, as
well as by slow southward-verging subduction of the Pacific plate
north of New Guinea at the New Guinea trench. Here, the
Australia-Pacific plate relative velocity is approximately 110 mm/yr
towards the northeast, leading to the 2-8 mm/yr uplift of the New
Guinea Highlands.
Whereas
the northern band of deformation is relatively diffuse east of the
Indonesia-Papua New Guinea border, in western New Guinea there are at
least two small (<100,000 km²) blocks of relatively undeformed
lithosphere. The westernmost of these is the Birds Head Peninsula
microplate in Indonesia's West Papua province, bounded on the south
by the Seram trench. The Seram trench was originally interpreted as
an extreme bend in the Sunda subduction zone, but is now thought to
represent a southward-verging subduction zone between Birds Head and
the Banda Sea.
There
have been 22 M7.5+ earthquakes recorded in the New Guinea region
since 1900. The dominant earthquake mechanisms are thrust and strike
slip, associated with the arc-continent collision and the relative
motions between numerous local microplates. The largest earthquake in
the region was a M8.2 shallow thrust fault event in the northern
Papua province of Indonesia that killed 166 people in 1996.
The
western portion of the northern Australia plate boundary extends
approximately 4800 km from New Guinea to Sumatra and primarily
separates Australia from the Eurasia plate, including the Sunda
block. This portion is dominantly convergent and includes subduction
at the Sunda (Java) trench, and a young arc-continent collision.
In
the east, this boundary extends from the Kai Islands to Sumba along
the Timor trough, offset from the Sunda trench by 250 km south of
Sumba. Contrary to earlier tectonic models in which this trough was
interpreted as a subduction feature continuous with the Sunda
subduction zone, it is now thought to represent a subsiding
deformational feature related to the collision of the Australia plate
continental margin and the volcanic arc of the Eurasia plate,
initiating in the last 5-8 Myr. Before collision began, the Sunda
subduction zone extended eastward to at least the Kai Islands,
evidenced by the presence of a northward-dipping zone of seismicity
beneath Timor Leste. A more detailed examination of the seismic zone
along it's eastern segment reveals a gap in intermediate depth
seismicity under Timor and seismic mechanisms that indicate an
eastward propagating tear in the descending slab as the negatively
buoyant oceanic lithosphere detaches from positively buoyant
continental lithosphere. On the surface, GPS measurements indicate
that the region around Timor is currently no longer connected to the
Eurasia plate, but instead is moving at nearly the same velocity as
the Australia plate, another consequence of collision.
Large
earthquakes in eastern Indonesia occur frequently but interplate
megathrust events related to subduction are rare; this is likely due
to the disconnection of the descending oceanic slab from the
continental margin. There have been 9 M7.5+ earthquakes recorded from
the Kai Islands to Sumba since 1900. The largest was the great Banda
Sea earthquake of 1938 (M8.5) an intermediate depth thrust faulting
event that did not cause significant loss of life.
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