Mammoth Lakes - New Eruption? 

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Monday, September 20th, 2004
Update at 8:00 AM (PDT) on Monday, September 20, 2004:
Earthquake activity within and adjacent to Long Valley caldera remains low with only one small (M<2)
earthquake detected and located by the realtime computer system in the last 24 hours.

Elsewhere, the earthquake swarm beneath the Adobe Hill 18 miles east of Mono Lake continues. As of this
update, it has included over 300 earthquakes since it began just after midnight on Sept. 18. Twenty three
of these have had magnitudes of M=3.0 or greater and five have had magnitudes of M=4.0 or greater.
The two largest earthquakes were M=5.5 and M=5.4 earthquakes at 4:02PM and 4:43 PM on the 18th.
The most recent M=3.0 earthquake occurred at 4:19 AM this morning (the 20th).
This update is from USGS Long Valley Observatory

The magnitude-5.5 temblor that struck at 4:02 p.m. Saturday, was followed by a magnitude-5.4 quake at 4:43 p.m. The moderate quakes were the biggest in the swarm and the biggest on the fault in more than a decade.
There were no immediate reports of any injuries or damage from the temblors centered along the
California-Nevada line about 30 miles northeast of Mammoth Lakes.

May 15th 1999 - Here we go again....
A magnitude 5.6 earthquake occured at 6.22 AM local time on May 15th 1999.
Epicenter was 8 miles WSW of Toms Place - 12 miles southeast of Mammoth Lakes.
The earthquake has been followed by quite a number of aftershocks, in fact as many as 760 during
the next 24 hours, of which at least 20 had a magnitude of 3.0 or greater, and four of 4.0 or greater.

 Date Local time Mag
 May 16th

 May 15th



Compare this table to the previous ones further down this page, having only 3-5 larger quakes per day.
However, USGS says that aftershocks can still be expected, up to 4 or 5, but the activity in the Long
Valley Caldera has not shown any increase in activity, so condition remains GREEN.

According to a CNN report there has been no damage or injuries.
But if it had occured in an urban area, it could have caused quite a bit of damage. If there is ever
a good place for an earthquake to occur, this is a good place, said a spokesman
for USGS i Menlo Park, California. The quake was however, the largest in 3 years..

Latest:  Jan.21st 1998:
Seismicity in the caldera declined to its lowest level in nearly two months, since the resurgence of activity along the south side of the caldera began on November 22. During the past week only 18 earthquakes occurred in the caldera that were as large as M2.0. Only two of these were as large as M3. This compares to the previous week when 75 M>2 earthquakes occurred, nine of which were as large as M3. (Copy from USGS)

December 14th, 1997 to Jan.5th 1998:
After three weeks of heavy activity, it seemed like it has calmed down. Week ending Dec.14th only had some 400 quakes over 1.5, and total quakes per day has fallen quickly. But then on Dec. 29th after a M 4.3 shock, it started all over again:

         last time                             this time
      total quakes   magnitude             total quakes    magnitude
      ------------   ---------             -------------   ---------
      Nov.30:    -    M 4.9                Dec. 29:  562   M 4.3, 3.0
      Dec. 1: 1805                         Dec. 30:  756   
           2: 1867    M 3.7,  M 3.2        Dec. 31:  785   M 4.8, 3.6, 3.7,
           3: 1918    M 3.8,  M 3.0                          3.3, 3,5, 3,5 
           4: 1941    M 4.0                Jan. 01: 1639   M 3.1, 3.8
           5: 1965**  M 3.2                Jan. 02: 1854   M 3.1
           6: 1935    M 3.0                Jan. 03: 2017   M 3.0, 3.0, 3.2
           7: 1887    M 3.0                                  3.6, 3.4  
           8: 1260                         Jan. 04: 2140   M 3.2, 3.6
           9: 1173    M 3.7                Jan. 05: 2302   M 4.1
          10: 1009    M 3.0                Jan. 06: 2363   M 3.1           
          11: 1011    M 3.7                Jan. 07: 2419
          12:  948                         Jan. 08: 1976
          13:  870                         Jan. 09: 1549   M 3.4, 3.6, 3.8
                                           Jan. 10: 1458   M 3.0
                                           Jan. 11: 1319   M 3.7, 3.2, 3.2
                                           Jan. 12: 1220
                                           Jan. 23:  255    quiet. 

Mammoth Lake has really been put  on the map, as swarms of earthquakes have hit the area for the past three weeks. Mammoth Lake is a beatiful summer/winter resort lying high up in the Sierra Mountains, just a few miles south of the famous  Yosemite National Park. As they say, you have to see it to believe it. Several links to the places further down the page...

According to reports from USGS (U.S.Geological Survey) this area has produced numerous volcanic eruptions over the last 3 million years, including a massive eruption 760.000 years ago. The most recent eruptions occured just 500 to 600 years ago along the Mono Crater-Inyo crater volcanic chain, which extends south from Mono Lake into the western part of Long Valley caldera.

During May 1980 a swarm of earthquakes hit the area, 4 of these had a magnitude 6, and that marked the onset of a period of unrest that continues up to now.
As illustrated in the ... some 20 small to moderate eruptions have occured along the Inyo-Mono Craters in the last 5.000 years. Does the new activity means that we can expect another eruption now? According to USGS the possibility is compareable with odds for a great (magnitude 8) earthquake occuring on the coast of California, and odds are smaller than for a major (magnitde 7 or greater) earthquake in L.A. or S.F. area.

However, as eruptions occurs every 250 to 750 years, the last big one was about 500 years ago, so why not now? Not that I want it, but IF it is coming, it's one of those nature wonders only happening once in a lifetime, and I don't want to read in the papers weeks later that I missed it. etc

Now, lets go back to Lake Mammoth again. This nice little community way up in the mountains, how do they feel about it? Quoting their electronic newspaper   Mammoth Times Online:
"Where else can one experience the thrill of an earthquake on earth without getting hurt? I think we have a new tourist attraction....We check out USGS website all day as we try to guess the magnitudes of each quake...". They say that they can feel any quake above 2.5 there, and sometimes they get several during only one day. On November 25th they had one at 3.0, one more the following day, and on the 30th of November a bigger one at 4,8, followed by 4 around 3,0-3,1.

Mammoth Lakes - new eruption?........
Updated map California/Nevada........
Long Valley location and background........
USGS Long Valley Caldera..................
USGS Long Term Outlook........
 Will have to look closer at this one for a while
 Up to the minute updates on map of California
 All you need to know.See FACT SHEETS,073-97
 Monitoring Volcanic Unrest, lots of info!
 LVc and Inyo-Mono Craters with links

Would like to keep myself informed. And it's interesting to see what is going to happen. I still remember SURTSEY off the coast of Iceland several years ago. So, if you think there is going to happen something more here, stay with me for a while...
I don't really understand much of what all those Volcanic-stations reports, but one thing is for sure - there is a lot of
eruptions around. Anyone else interested in following, please get in touch!

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