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Pago Pago (Samoa) Site History

History Summary

Please note that the position information has been altered in this document - see document 83916

Reference Level

All heights have been referred to the station tide staff zero which is linked to fixed benchmarks.

Tide Gauge Benchmark (TGBM) Description

Benchmark M 1983 the primary benchmark is stamped '0000 M 1983', and is set in a bedrock outcrop at the southern most corner of the wall surrounding the Government Estate.

Auxiliary Benchmarks

Eight additional benchmarks are levelled to the TGBM and the Tide Station on a yearly basis.

Benchmark Relationships

TGBM is 13.20 feet above the Tide Gauge Zero (Station Datum).

NOAA Chart Datum (MLLW) is 2.48 feet above the Station Datum.

Mean Sea Level (1960-1978) is 3.83 feet above the Station Datum.

Quality Assessment by the UH Sea Level Center

Comment

Reference level shifts were adjusted by adding the following to the original data:

• (-5 cm) 09Z 12 February - 22Z 20 February 1975
• (7 cm) 23Z 20 Febraury - 02Z 02 March 1975

Otherwise, the daily and monthly means in comparison with Apia suggest a level shift of about +12 cm on 1 August 1993 and of about -12 cm on 1 January 1995. This signal is under investigation by the originatiors.

The data for 1996-2000 were supplied with heights relative to MLLW. Consequently 759mm was added to refer the data to tide gauge zero.

The data for 1998-2000 were supplied in non-GMT format and had to be shifted into GMT.

Notable episodic events:

• 04-06 November 1952: Tsunami from Kamchatka
• 09-10 March 1957: Tsunami from C. Aleutians
• 23-25 May 1960: Tsunami from S.C. Chile
• 28 March 1964: Tsunami from Alaska
• December 1991: Cyclone Val

Gaps in the Data Record

The following gaps occur in the data set.