Earthquake Commentary for September, 2000

Map of recent earthquake activity

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08:28 PDT, Friday, September 29

A quake at 2:57 am this morning was felt in the general area of Borrego Springs. The magnitude was M3.5 and the epicenter was located 8 miles east-northeast of Borrego Springs. The focal mechanism is mostly strike-slip.

18:42 PDT, Thursday, September 28

The week's earthquake list totals 390 this week. Click here to see a summary and map .

09:23 PDT, Thursday, September 28

A swarm of earthquakes occurred in northern Baja yesterday evening between 9 and 10 pm. The largest was a M4.1, located 76 miles south of Ocotillo. Because of the distance, it seems unlikely that this quake was felt in the U.S.. We have had other quakes in northern Baja this week, but none this large.

08:30 PDT, Monday, September 25

There was another small, but felt, quake last night: a M3.1 at 9:00 pm, located 4 miles north-northwest of Claremont. It was felt widely in the Inland Empire area.

14:31 PDT, Sunday, September 24

We dectected 7 earthquakes M3.0 or greater this weekend, but only one was located in southern California. This earthquake, a preliminary M3.4, occurred at 11:34 am (PDT) today and is located 22 miles north of Joshua Tree. It is an aftershock to the M7.1 Hector Mine mainshock of October 16th, 1999. The remaining 6 earthquakes all occurred south of the border in Baja California ranging from 40 to 60 miles south-southwest of Calexico, California. They are listed in order from present to past (and ALL are preliminary in size, location and time): M3.2 at 6:03 pm Saturday, M3.5 at 4:51 pm Saturday, M3.2 at 3:51 pm Saturday, M3.5 at 12:34 pm Saturday, M3.0 at 11:50 am Saturday, and M3.0 at 10:54 pm Friday.

11:55 PDT, Friday, September 22

The week's earthquake list totals 368 this week. Click here to see a summary and map .

12:54 PDT, Thursday, September 21

The U.S. Geological Survey in Menlo Park has reported two small quakes this morning, located 4 miles south-southeast of Parkfield. These two quakes, which you can see on the above "Recent Earthquakes" link, were a M3.3 at 11:08 am and a M3.0 at 11:09 am. Parkfield is a small town about halfway between Los Angeles and San Francisco. It is directly on the San Andreas fault and is famous as a sort of "living earthquake laboratory", due to the large number of seismic and other instruments installed there.

There has also been a small quake on the opposite "fringe" of our seismic network, 35 miles south-southeast of Ocotillo, in Mexico. Magnitude was M3.1, and the time was 12:21 pm today. It is unlikely that anyone in the U.S. felt this earthquake.

07:46 PDT, Thursday, September 21

Another Hector aftershock occurred last night at 8:06 pm. The magnitude was M3.2, and the epicenter was located 27 miles north of Joshua Tree. It was not, as far as we know, felt.

13:02 PDT, Wednesday, September 20

This morning, there was also a M3.1 Hector aftershock. The time was 11:57 am and the epicentral location was 24 miles north of Joshua Tree. Due to the remote location, we do not expect to get inquiries.

09:58 PDT, Wednesday, September 20

At 9:10 am this morning, a M3.8 quake occurred in the Rose Valley area, 3 miles east of Coso Junction. There was some activity in this area yesterday. As the Coso region is prone to swarms of quakes, we will be keeping an eye on it. Swarms consist of anywhere from dozens to hundreds of small quakes (M1's, M2's, and M3's). In some swarms, there are also a few members as large as the lower M5's. Although we have no "felt" reports on today's M3.8 as yet, due to its size, it was probably felt through the southern Owens Valley area.

09:26 PDT, Tuesday, September 19

Southern California experienced two M3+ quakes last night. The first was a M3.0 quake in the Rose Valley area, 4 miles east of Coso Junction, at 8:46 pm. It seems to have gone unnoticed by the public.

The second quake was a M3.1 in the San Gorgonio Pass area, 3 miles north-northwest of Cabazon. Time was 3:17 am. It was felt in Forest Falls and Idyllwild.

07:57 PDT, Monday, September 18

A small quake (M2.8) occurred in the northern Imperial Valley very early this morning, at 3:24 am. The epicenter was 2 miles east-northeast of Obsidian Butte. There were no "felt" reports.

12:48 PDT, Saturday, September 16

Two quakes of note occurred overnight in southern California. The first was a M3.7 Hector aftershock at 11:28 pm. The epicenter was located 30 miles southwest of Baker. Although we have no inquiries, I would be surprised if it was not felt in Baker and Barstow.

There was also a quake in Marina Del Rey this morning, at 6:24 am. This one was moderately widely felt in the Los Angeles area. "Felt" reports came from Marina Del Rey, and as far away as Sherman Oaks, Hollywood, and Hermosa Beach. Although, judging from our web hit statistics, it must have jangled a lot of people's nerves, the magnitude was only M3.3. If you felt it and would like to add your experiences to the data base, go to the Community Internet Intensity Map

A third quake above M3 occurred at 3:30 am, 39 miles south-southwest of Calexico, in Mexico. Magnitude was M3.4. Although it is possible that this quake could have been felt in the Imperial Valley, we have received no reports that it was.

18:51 PDT, Thursday, September 14

The week's earthquake list totals 351 this week. Click here to see a summary and map .

08:50 PDT, Thursday, September 14

A pair of M3.2 quakes occurred last night. The first one was at 1:26 am, located 36 miles south-southeast of Ocotillo, in Mexico. It might possibly have been felt in the U.S., so I list it.

The other M3.2 was definitely in the U.S., 6 miles north-northeast of Ocotillo. The time was 4:17 am.

There was also a M2.5 in the Coso Range area, 7 miles east-northeast of Coso Junction, at 12:25 am. We had no public inquiries about any of the overnight quakes.

09:34 PDT, Tuesday, September 12

There were two feelable quakes early yesterday evening. The first was a M3.1 Hector aftershock, located in the northern part of the aftershock zone, 34 miles southwest of Baker. Time was 5:22 pm. The second quake was a M3.6 at 6:07 pm, located 9 miles east of Ocotillo or 17 miles west-southwest of El Centro. The Ocotillo quake was felt.

There was another small quake at 9:12 pm, located 3 miles north-northeast of Big Bear City. Magnitude was M2.9. We've had no inquiries about that one.

The widely felt (from Long Beach to Malibu) "event" around noon yesterday did not trigger our seismic network. Our best guess from the descriptions is that it was a sonic boom that was felt.

09:17 PDT, Monday, September 11

Earthquakes this weekend included a M3.1 over the border in Nevada, on Nellis Air Force Base, 43 miles northeast of Furnace Creek (Death Valley). This quake occurred on Saturday, at 12:12 pm. If it was felt, it was not reported.

Another small quake occurred on Sunday at 12:53 pm, in the Coso Range, 7 miles east-northeast of Coso Junction. We have no inquiries about that one, either.

Finally, at 7:29 am this morning, there was a M2.9 quake 9 miles southwest of Ocotillo, near the U.S./Mexico border, very near Inkopah County Park. We have no inquiries about this one either.

17:22 PDT, Thursday, September 07

Seismicity has been very quiet this week, at least in southern California. The largest quake that we've had was the M3.2 Hector aftershock at 12:34 pm this afternoon. It's epicenter was located 30 miles south-southwest of Baker.

The week's earthquake list totals 216 this week. Click here to see a summary and map .

11:35 PDT, Monday, September 04

A M2.9 quake occurred this morning at 10:27 am, in the Big Bear area. The epicenter was located 3 miles north-northeast of Big Bear City. It was lightly felt in Big Bear City.

20:31 PDT, Saturday, September 02

A M2.6 quake occurred this afternoon at 2:57 pm, located 5 miles east of Cabazon. We have no "felt" reports.

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Last updated 08:28 PDT September 29, 2000.