Baja Continues to Shake

The sequence of earthquakes coming out of Northern Baja is quite impressive and is not showing any signs of slowing down. It resembles an aftershock sequence you might see after a 6+ earthquake. But there was no 6+ earthquake. In fact, the quake which started this was only a 5.4.

The quake was originally posted as a 5.4 and later downgraded to a 5.1. There is still some debate over the true magnitude of this quake. It will take some time to determine the actual magnitude. It should be somewhere between 5.1 and 5.5.

As of the time of this report the 5.4 quake has been followed by at least 35 aftershocks with a magnitude of 3.0 or greater. Five have been greater than 4.0 and two have been 5.0 or greater. In total there have been over 200 aftershocks.

How does this compare with previous quakes in the area? Data from previous years shows that in May of 2006 a 5.4 earthquake produced 16 aftershocks of 3.0 or greater. In February of 2002 a 5.7 quake in the same area produced nearly fifty 3.0+ aftershocks.

The question that I'm sure everyone is asking is whether something bigger and more destructive is on the way. Nobody can say for sure. The 5.7 quake in 2002 was preceded by increased seismic activity which started in December of 2001.

It is always best to be prepared. Plan as if a stronger quake is on the way. Make sure you are prepared by having a supply of bottled water and non-perishable food. Always sleep with a pair of shoes and a flash light near your bed. Make sure there are no loose items or furniture that could fall and hurt someone.

It's a good idea to always be prepared. The mainshock is usually the largest and most destructive, and waiting until after the mainshock to get prepared is a bad idea.

Here is a link for more tips on how to prepare for an earthquake and what to do after one strikes.ALWAYS BE PREPARED

Here is our latest image showing the region affected by these quakes (click on it to enlarge):

Obsidian Butte: Swarm Update

UPDATED: 9/5/05 - 3:00 AM

NEXT UPDATE: 9/10/05 (unless there is a significant increase in activity)

NOTE: This report focuses on a very small radius (20km) around Obsidian Butte and does not include the entire Brawley Seismic Zone.

CURRENT SWARM STATS:
Total Quakes (8/25 - 9/5 2:15am) = 626

dates
8/25 = 1 quake
8/26 = 0 quakes
8/27 = 0 quakes
8/28 = 8 quakes
8/29 = 15 quakes
8/30 = 2 quakes
8/31 = 220 quakes
9/1 = 251 quakes
9/2 = 80 quakes
9/3 = 34 quakes
9/4 = 11 quakes
9/5 = 4 quakes (preliminary)
These quake counts are likely to change with time as USGS officials manually review seismographs.

magnitudes
0.1 - 0.9 = 2 quakes
1.0 - 1.9 = 426 quakes
2.0 - 2.9 = 165 quakes
3.0 - 3.9 = 25 quakes
4.0 - 4.9 = 7 quakes
5.0+ = 1 quake


Obsidian Butte is one of several areas in California known for its earthquake swarms. Unlike The Geysers in Northern California and Coso Junction in Central California, Southern California's Obsidian Butte is sporadic and inconsistent with its swarming. While the other swarm areas rarely see days without quakes, Obsidian Butte can go months without registering a single quake. But when they come, they come in a big way. However, when the quakes do come, they come in volume and not strength.

Obsidian Butte is not known for producing large destructive quakes. Obsidian Butte has seen thousands and thousands of quakes over the years (nearly 10,000 since 1960). However, since 1900 there has only been a handful of quakes that have been stronger than a 5.0. The largest being a 5.8 in 1981. That was also the last time a 5.0 or larger quake was centered in the vicinity of Obsidian Butte.

HERE is a map
showing all 5.0+ quakes that have occurred near the Salton Sea since 1900. On the map you will notice that there are just a few quakes in the immediate area of Obsidian Butte. All Obsidian Butte swarms occur tight against the South-East shoreline of the Salton Sea.

This swarm is following a classic pattern. Reviewing past swarm data shows that this one is making a run to be one of the strongest in many years.

we have seen some impressive swarms since 1960. Here is a list of the most active months (minimum of 50 quakes):

APR 1981: 1250 quakes
SEP 2005: 380 quakes (preliminary)
AUG 2005: 285 quakes (preliminary)
MAR 1989: 248 quakes
NOV 1976: 239 quakes
MAY 1981: 184 quakes
JUN 1979: 169 quakes
NOV 1987: 162 quakes
JUL 1987: 152 quakes
MAY 1983: 130 quakes
OCT 1999: 112 quakes
MAY 1996: 107 quakes
OCT 1979: 105 quakes
JAN 1998: 94 quakes
APR 2003: 88 quakes
MAY 2000: 86 quakes
JUN 2000: 83 quakes
MAR 2004: 77 quakes
JUL 1983: 76 quakes
AUG 1996: 75 quakes
FEB 1989: 69 quakes
DEC 1997: 67 quakes
DEC 1988: 58 quakes
AUG 1986: 56 quakes
OCT 1988: 54 quakes
FEB 2002: 53 quakes
OCT 1995: 51 quakes
JUL 1992: 50 quakes
SEP 2003: 50 quakes


April 26, 1981 was most likely the most active day for swarm quakes at Obsidian Butte. 609 earthquakes were recorded on that day. This day also saw the strongest swarm related earthquake which was a 5.8.

Interestingly there has only been three, maybe four quakes above 5.0 at Obsidian Butte since 1900. We have already talked about the largest, a 5.8 on April 26, 1981. The others were a 5.1 on November 4, 1976 and a 5.5 on July 29, 1950.

The 5.1 in 1976 was also in the middle of a swarm. That particular swarm started at 04:57 with a 2.6 quake. The 5.1 occurred at 10:41 and was the 42nd quake to occur in the sequence. This 1976 swarm died out by the end of November with a total quake count of over 200.

Here is a list of all Obsidian Butte quakes with a magnitude of 4.0 or higher. There really isn't very many considering Obsidian Butte has been the host to nearly 10,000 earthquakes since 1960.

5.8 4/26/81
5.1 9/1/2005
5.1 11/4/76
4.7 10/16/99
4.6 8/31/2005
4.6 3/6/89
4.5 9/1/2005
4.5 8/31/2005
4.5 10/16/99
4.5 8/31/2005
4.4 8/31/2005
4.4 7/13/83
4.4 11/4/76
4.3 8/31/2005
4.2 11/4/76
4.2 11/4/76
4.2 10/27/63
4.2 10/19/88
4.1 8/31/2005
4.1 6/13/79
4.1 11/4/76
4.1 11/4/76
4.1 11/4/76
4.1 11/4/76
4.0 12/31/97
4.0 4/26/76

CURRENT SWARM REPORT
This report will be updated periodically to reflect new quakes. The map below (click for larger view) shows only quakes from this current swarm. These quakes will not be added to the main maps and lists until their magnitudes and locations have been reviewed and updated.



CURRENT OBSIDIAN QUAKES OF 3.0 AND GREATER
click here to see all quakes

3.7 9/5/2005 1:53 AM 1E Obsidian Butte, CA
3.0 9/3/2005 4:17 AM 1ENE Obsidian Butte, CA
3.4 9/1/2005 11:44 PM 1ENE Obsidian Butte, CA
3.3 9/1/2005 8:55 PM 3SSW Obsidian Butte, CA
3.3 9/1/2005 8:54 PM 2SSW Obsidian Butte, CA
3.1 9/1/2005 8:50 PM 1SW Obsidian Butte, CA
3.2 9/1/2005 8:46 PM 2SW Obsidian Butte, CA
3.7 9/1/2005 7:46 PM 1SSW Obsidian Butte, CA
3.0 9/1/2005 6:38 PM 1SSW Obsidian Butte, CA
3.8 9/1/2005 6:30 PM 2WSW Obsidian Butte, CA
5.1 9/1/2005 6:27 PM 1S Obsidian Butte, CA
4.5 9/1/2005 6:27 PM 0NE Obsidian Butte, CA
3.0 9/1/2005 6:23 PM 2E Obsidian Butte, CA
3.2 9/1/2005 7:06 AM 3NE Obsidian Butte, CA
4.4 9/1/2005 6:50 AM 1NNE Obsidian Butte, CA
3.6 9/1/2005 6:50 AM 0E Obsidian Butte, CA
3.5 9/1/2005 6:48 AM 1E Obsidian Butte, CA
3.1 9/1/2005 1:24 AM 1E Obsidian Butte, CA
3.1 8/31/2005 9:15 PM 1ENE Obsidian Butte, CA
4.5 8/31/2005 4:32 PM 3ENE Obsidian Butte, CA
3.4 8/31/2005 4:29 PM 2E Obsidian Butte, CA
4.3 8/31/2005 4:27 PM 3ENE Obsidian Butte, CA
4.1 8/31/2005 4:07 PM 1ENE Obsidian Butte, CA
3.1 8/31/2005 3:59 PM 0ESE Obsidian Butte, CA
3.2 8/31/2005 3:54 PM 1SSE Obsidian Butte, CA
4.5 8/31/2005 3:50 PM 2E Obsidian Butte, CA
4.6 8/31/2005 3:47 PM 1SSE Obsidian Butte, CA
3.5 8/31/2005 3:45 PM 1E Obsidian Butte, CA
3.1 8/31/2005 3:17 PM 1E Obsidian Butte, CA
3.1 8/31/2005 2:49 PM 1NE Obsidian Butte, CA
3.4 8/31/2005 9:18 AM 3ENE Obsidian Butte, CA
3.7 8/31/2005 8:35 AM 2NE Obsidian Butte, CA
3.1 8/29/2005 12:39 AM 4NE Obsidian Butte, CA




Here are some links to articles about the swarm:
Is there a relationship between the Salton Sea earthquake swarm near Obsidian Butte and the hurricane Katrina? (conscious junkyard)

Kate Hutton Earthquake commentary (SCSN)

SCSN Special Report (SCSN)

IS BAJA READY?

Those that study patterns of small earthquakes to help predict the next significant earthquake may want to take a look at Northern Baja California. The area in question is located about 45-50 south of the California border in central Baja California.

I have noted an area where five quakes have occurred over the last few weeks. I have compiled a 25-year list of earthquakes that have occurred within a 15 mile (26.5 km) radius of where these quakes have occurred. (NOTE: All quakes referenced in this report are of 3.0 or greater)

This area has a rich seismic history, but has been very quiet in recent years. Prior to these recent quakes, a 3.0 was recorded on December 13th of 2004.

This area has seen four earthquakes of 5.0 or higher in the last 25 years. The most recent was a 5.0 on 12/3/91. The other three were all 5.1 and they occurred on 8/31/88, 1/25/88 and 5/8/85. Three of the four had at least one notable foreshock.

The 5.0 of 12/3/91 had two quakes within about six weeks of the mainshock, but calling these foreshocks might be a stretch based on this data.

The 5.1 of 8/31/88 had a 3.3 foreshock four days prior and a two other small 3's within a few weeks.

The 5.1 of 1/25/88 saw seventeen foreshocks. Activity increased in August of 1987 and four significant foreshocks occurred within the month prior to the mainshock. Before August, the last quake was back at the end of January.

On May 8, 1985 there was a 3.3 foreshock followed by a 5.1 mainshock about two hours later.

Although having 4 quakes in this area in a short period of time is not unprecedented, it is something to keep an eye on. Larger quakes here tend to have foreshocks.

HERE is the complete list of quakes that was used for this report.