[Geysers] Seismographs

[Mike Keller]

Here is what I can tell ya:

1-Giantess, over the years, I have seen show up one of two ways on the
seismograph.  The first, which is how this eruption appeared, is what
appears to be a steady small earthquake lasting from 15-45 minutes.  It
takes about 15 minutes per revolution of the seismograph at the OFVC and
this last eruption is measured for just over 2 turns.  The second type looks
more like a series of earthquakes over this same time span, with clear
breaks between events.  I remember Rick Hutchinson mumbling in the past when
there was a lot of tremor swarms/seismic activity it was much harder to
single out Giantess from a small quake.

As for magnitude, I don't know the exact reading.

2-Giant has had eruptions in the past that have thumped the platform and
rattled signs.  I witnessed this on the 12/18/88 eruption and I believe Lynn
Stephens saw the same in prior to the 9/12/88 eruption.  This same
phenomenon was described by several observers in the late 1880's.  I have
been at the platform or arrived within a few minutes of the start of over 50
Giant eruptions in the past 15 years and the eruption on 12/18/88 was the
only time I have felt this phenomenon.

MK

-----Original Message-----
From: geysers-bounces at wwc.edu [mailto:geysers-bounces at wwc.edu] On Behalf Of
Jeffrey Cross
Sent: Sunday, January 30, 2005 8:32 PM
To: geyser observation reports
Subject: [Geysers] Seismographs

Several questions:

1) When Giantess registers on the seismograph, how big of an eartuquake
does it create?  M 2.0?  1.0?

2) Years ago I remember hearing that prior to Giant Geyser's eruptions,
the platform would shake and pound.  Yet I have not heard anybody mention
this for perhaps the last 15 years.  Did this really happen?  And if so,
does it still happen?

3) Does anyone have the URL for the Yellowstone photo files?  It appeared
on the list last winter, but I have since lost it.

Assuming I did not miss finding it on the GOSA website, it would be a nice
additional link.

Jeff Cross
jacross at lamar.colostate.edu


On Sun, 30 Jan 2005, Mike Keller wrote:

> Giantess was first seen at 0826ie by NPS Ranger Carolyn Loren (forgive me
if
> I misspelled your name!).  From the seismograph it appears to have started
> around 0200.
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