From: jester@crash.cts.com (Ken Bibb)
Newsgroups: ca.earthquakes
Subject: Questions raised by SoCal Activity
Keywords: usgs refs, landers
Date: 15 Aug 92 18:45:11 GMT
Reply-To: lee@bnf.com


My father, lee@bnf.com, doesn't have direct access to this newsgroup, so
he asked me to post this for him.  If you reply to me, I'll forward the
mail to him.  The Reply-to: header line should work (shouldn't it?) to
forward any replies directly to him.

Posts are preferred to personal email.

The following is an open letter, originally to be sent to andy@pangea, but
I talked my father into posting it instead...

---------

1)  Refer to book _Earthquake_Hazards_in_the_Los_Angeles_Region,
    USGS, 1985, map pages 34 and 35 showing "...1970 to 1981 record of
    well-located epicenters of M>=3 earthquakes...".  Note the number
    of epicenters along the Desert Hot Springs-Yucca Valley-Landers
    alignment, so well known now since June 28.  Also note the cluster
    of epicenters around Lat N 34 35' Long W 116 18' compared to
    recent activity.  What would a similar map for 1981 to 1991 show?
    If the 1970-1981 level of activity was maintained through the
    80's, should such areas of high seismic activity be placed on some
    alert basis?  It appears that the June 28 earthquake was
    telegraphed for several decades.  Are there other areas in
    California where similar long-term clusters of epicenters might
    indicate future large-scale earthquakes (other than Long Valley
    Caldera)?  Are such observations a part of the development of a
    method of seismic prediction?  Why is a relatively quiet portion
    of a fault considered to be a risk when the Landers experience
    shows a great deal of activity may instead be the precursor of a
    major quake?

2)  At the end of the California portion of "The Making of A
    Continent" there is a computer generated map with a 'clock'
    showing millions of years.  This map proposes that in about 3
    million years all of California west of the Sierra Nevada fault
    and our recent Desert Hot Springs-Yucca
    Valley-Landers-Barstow-Ridecrest line of epicenters will swing out
    on the Pacific Plate and drift off to the north.  Why, the, all of
    the media attention to northward movement just westerly of the
    currently-designated San Andreas Fault?

3)  Can you give me references for the role of plate tectonics in the
    creation of the Sierra Nevada, Owens Valley, White and Panamint ranges
    and Death Valley?  Note:  The Front Range of the Rocky Mountains also
    lines up between the Mendocino and Murray fracture zones projected
    eastward.  Has the eastward movement of the Sierra Nevada stopped?  Is
    that why the beginnings of movement with the Pacific Plate?

4)  A glance at the map of North America shows:
	a) a row of volcanos inland from a subduction trench from the
	   Straits of Juan de Fuca to Cape Mendocino
	b) The North American Plate overrides the Pacific Plate and
	   then is carried back eastward on the Pacific Plate from
	   Cape Mendocino to Point Concepcion
	c) From Point Concepcion to the Salton Basin is
	   faulting--sliding along a subducted fracture zone
	d)  the Salton Basin/Gulf of California spreading, with a
	    portion of the Cocos (?) Plate carrying northern Mexico. 
	
    A reference, please, for the location of the East Pacific Rise
    under California.
--
lee@bnf.com		Leland E. Bibb		Meridian Land Surveying
						(619)589-7008