July 3 1999 (July 2 local time) Satsop Earthquake
Basic Information
Time of Occurrence (GMT): Saturday July 3, 1999 at 01:43:54.33 Z
Time of Occurrence (PDT): Friday July 2, 1999 at 06:43:54.33 PM
Time of Occurrence (PST): Friday July 2, 1999 at 05:43:54.33 PM
Depth (km) 40.57
Magnitude: Mw=5.8 (Harvard CMT) Other magnitude estimates: MS=5.5, mb=5.5, Mc=5.1
Location 47.0757N 123.4635W
8.2 km N of Satsop, WA
28.9 km ENE of Aberdeen, WA
103.5 km WSW of Seattle, WA
Name of data file: 99070301435p
A Note on The Magnitude
The magnitude estimation routinely used by the Pacific Northwest Seismograph Network is Mc or "Coda magnitude".
Although the
coda magnitude scale works well for small and moderate size earthquakes
it has not been well calibrated for deep and large earthquakes. In order to
do a better job of comparing this earthquake with other large earthquakes
around the world it is useful to determine the magnitude using other methods
commonly used for large earthquakes. Coda magnitude for the Satsop earthquake
is Mc 5.1
Other
magnitude scales include
the body wave magnitude (mb), surface wave magnitude (Ms) and moment magnitude
(Mw). Other agencies including the National Earthquake Information Center,
and Harvard University have computed the following
estimates of magnitude for this earthquake: mb=5.5, Ms=5.5, and Mw=5.8.
Earthquake Felt Reports for the Main Shock
Summary of Felt Reports received for this earthquake (includes an intensity map).
Aftershocks
Normally, deep earthquakes have very few significant aftershocks.
This earthquake had no detectable aftershocks for several days.
On July 9, 1999 we recorded 3 small aftershocks with epicenters and
depths almost identical to the main shock. They included earthquakes
at 05:13UT (Mag 1.6), 07:45UT (Mag 2.5), and 08:07UT (Mag 2.3).
Detailed Information and Graphics for the Main Shock
Our data base of earthquake hypocenters contains information
from the 19th century to the present.
Included are:
- A regional map showing the location of
the earthquake (in red) plus previous earthquakes M > 3.5 since 1990.
- A Intermediate scale map
showing the location of the earthquake and prior historical earthquakes
with magnitude 3.5 or greater.
- A list of 10 big earthquakes
preceding the mainshock that are closest to it and have a
magnitude greater than 3.5. These are the most significant
historical earthquakes in the vicinity of the mainshock
(see intermediate scale map above).
- A map showing
the location of the earthquake relative to cities.
- A map showing
the location of the earthquake relative to the nearest
seismograph stations that recorded it.
- A detailed list of all earthquakes
(M > 1.0) that occurred in the vicinity of the special earthquake
in the previous two years. For the locations of these events see
the next map.
- A map of all earthquakes
(M > 1.0) that occurred in the two years prior to the special earthquake.
Detailed area shown is just few kilometers around the mainshock.
- A List of the nearest 20 strong motion sites
Earthquake Mechanism
If sufficient P-wave first motion data are available,
a fault plane determination for the earthquake
will be available in the form of
Moment Tensor Estimates of the Earthquake size may also be available. To see,
check at Oregon State U.
Preliminary Strong Motion Information
Related Information: Most Up-to-Date Local, National, and Global Earthquake Summaries