Earthquake Commentary for March, 1999

Map of recent earthquake activity

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17:59 PST, Wednesday, March 31

We just had a few small quakes in the Ocotillo area. They were: a M3.1 at 4:49 pm, another M3.1 at 4:54 pm, and a M2.8 at 5:05 pm. The epicenters were all in Mexico, 15 miles southwest of Ocotillo, but they may have been felt in Ocotillo and surrounding communities.

08:28 PST, Wednesday, March 31

This morning's only seismic action occurred at 7:24 am, 18 miles north of Yucca Valley. The magnitude was 2.6. This quake was a Landers aftershock, in a remote area.

12:54 PST, Monday, March 29

This morning, at 9:49 and 9:59 am, there were two small quakes 4 miles north of Big Bear City. The magnitudes were M2.5 and M2.6, respectively.

At 5:50 pm yesterday afternoon, there was a M2.7, located 7 miles northwest of Arvin.

Earlier yesterday, there was a small (M2.5) Landers aftershock, located 8 miles southeast of Yucca Valley.

The largest quake of the weekend was a M3.4, 5 miles southeast of Perris, at 4:12 pm on Saturday. We haven't gotten any inquiries, but I would be surprised if it was not felt by someone.

05:37 PST, Friday, March 26

We recorded and analysed 154 earthquakes in the past week. Click here to see a summary and map .

11:04 PST, Thursday, March 25

There was a small Landers aftershock at 10:20 am this morning, located 9 miles south of Joshua Tree. The magnitude was M2.8. We have received no inquiries, which is not surprising, as the epicentral area is a remote one.

09:44 PST, Monday, March 22

We received several in inquiries this morning about a M3.8 quake at 12:31 am, located 2 miles southeast of Loma Linda, or 3 miles west-southwest of Redlands. The epicenter is close to the intersection of the Banning Fault, a branch of the San Andreas, and the San Jacinto Fault, and is a very common source of small earthquakes. In this case, however, the focal mechanism was thrust, on a plane that strikes nearly north-south, which is inconsistent with either of these two big faults. This morning's quake must therefore have occurred on some minor nearby fault. There was a small handful of aftershocks, the largest of which was a M2.5 at 12:39 am.

Other mentionable quakes over the weekend include: a M2.8 at 6:17 pm Sunday, 8 miles west of Trona; a M2.7 at 3:31 pm Sunday, located 5 miles north of Big Bear City; and a M3.1 at 5:53 am Sunday, located 4 miles north-northeast of Lake Isabella. We got no inquiries about any of these events.

10:34 PST, Friday, March 19

At 8:48 am this morning, the northern Imperial Valley experienced a M2.8 quake. The epicenter was a common one, 2 miles northeast of Obsidian Butte, in the Brawley Seismic Zone. It was the largest member of a small swarm of about a dozen events.

Also of possible interest: a M2.4 that occurred at 1:48 am today, located 2 miles north of Signal Hill, near the Newport-Inglewood Fault, and a M2.4 Landers aftershock, 8 miles north-northeast of Barstow, at 2:46 am.

There have been no "felt" reports for any of these quakes.

17:16 PST, Thursday, March 18

We recorded and analysed 185 earthquakes in the past week. Click here to see a summary and map .

08:49 PST, Tuesday, March 16

The only action since the last update was a M2.7 at 1:08 pm yesterday, located 11 miles north of Ridgecrest, near China Lake. This epicenter is close a M5.8 that occurred in September of 1995.

10:02 PST, Monday, March 15

At 8:24 am this morning, a M3.1 quake occurred offshore, 12 miles north of Santa Barbara Island, or about 30 miles south of Pt. Mugu. Because of its location, we don't expect to hear any "felt" reports.

Yesterday, there was also some activity south of the U.S./Mexico border. Only a couple of these quakes could possibly have been felt in the U.S.: a M3.0 at 8:49 am Sunday, located 27 miles southeast of Calexico, and a M2.9 at 12:56 am today, located 18 miles south-southeast of Calexico.

Another M2.9 occurred at 6:45 am on Sunday, this time 4 miles north-northeast of the town of Lake Isabella. We've had no inquiries, but the quake could have been felt at Lake Isabella.

11:22 PST, Saturday, March 13

The biggest event overnight was a M4.3 quake, located 15 miles southwest of Ocotillo, at 5:31 am this morning. The focal mechanism is strike-slip, with almost north-south and east-west planes. Note that we have seen several other events in this area in the last month, including a M4.2 and a M3.5 on the evening of February 18. Today's quake was felt in El Centro.

Also perhaps of interest, there was a M2.6 in the San Jacinto Fault zone, 8 miles east of Borrego Springs, at 7:30 pm yesterday.

Later this morning, at 6:22 am, there was a M2.6 located 12 miles south-southeast of Barstow. Interestingly, this location has not been active in the Landers aftershock sequence, so this morning's quake must not be an aftershock.

16:53 PST, Thursday, March 11

We recorded and analysed 159 earthquakes in the past week. Click here to see a summary and map .

09:19 PST, Thursday, March 11

There was a M3.0 this morning at 7:11 am, an aftershock of the Whiskey Springs (M4.9 October 28, 1998). We do not know if it was felt or not.

08:36 PST, Wednesday, March 10

There was a M2.6 at 2:26 am this morning, located 25 miles east-northeast of Lucerne Valley. It was an aftershock of the June 28, 1992 Landers earthquake (Mw7.3). Due to the remote area, it was almost certainly not felt.

09:38 PST, Monday, March 08

There was a small cluster of activity in the Newhall area early this morning. The largest events were: a M2.7 at 2:52 am, a M2.0 at 3:26 am, a M2.2 at 4:03 am, and a M3.0 at 4:09 am. They were located about 4 miles north-northwest of San Fernando, or 4 miles southeast of Newhall, putting them within the Northridge earthquake aftershock zone. The focal mechanism of the largest event (M3.0) was thrust. We assume that at least the M3.0 was felt by someone, but we haven't received any inquiries.

There was also some minor action in the Anza-Borrego area over the weekend: a M2.7 at 7:50 am on Sunday, located 7 miles north-northwest of Borrego Springs, probably associated with the complex San Jacinto Fault zone. As far as we know, this quake did not attract any attention, either.

09:47 PST, Friday, March 05

Yesterday evening's quake was a M3.5, located 8 miles east of Desert Hot Springs, in the Joshua Tree National Monument. It occurred at 10:13 pm, and was felt in the Desert Hot Springs and Palm Springs area. It is an aftershock of the Landers earthquake (Mw7.3 on June 28, 1992). The focal mechanism appears to be mostly strike-slip.

17:30 PST, Thursday, March 04

We recorded and analysed 134 earthquakes in the past week. Click here to see a summary and map .

12:30 PST, Thursday, March 04

There was a M3.0 quake this morning, at 11:34 am, 9 miles east-southeast of Ridgecrest. This epicenter is about 6 miles away from the Garlock fault, so probably not associated with that fault. The focal mechanism shows strike-slip faulting.

13:39 PST, Wednesday, March 03

At 1:06 pm yesterday, there was a small quake (M2.5) located 5 miles south of Ojai. Also, at 7:20 am today, there was another one (also M2.5), 5 miles southwest of Valencia. The second quake was a Northridge aftershock. Neither of these was reported felt.

08:19 PST, Tuesday, March 02

Yesterday afternoon, there was a M2.6 near Loma Linda (2 miles west-southwest of Loma Linda), at 2:34 pm. As far as we know, it was not felt.

Another small quake occurred this morning at 3:56 am. It was located 4 miles north-northeast of Rialto, and had a magnitude of M2.5. We do not believe that it was felt, either.

10:51 PST, Monday, March 01

There were a few events of minor interest over the weekend:

First, a M3.5 in northern Baja, 40 miles southeast of Calexico, at 2:31 pm on Saturday.

Second, a M2.6 Landers aftershock at 6:30 pm on Saturday, located 11 miles south of Joshua Tree.

Third, a M2.7 in the Ococtillo sequence, 4 miles east-southeast of Ococtillo. The time was 10:51 pm on Saturday. These first three were probably not felt.

Fourth, a M2.6 at 9:51 pm on Sunday, located 3 miles northeast of Baldwin Hills. In spite of its small size, this one was felt.

And finally, stretching the limit of reportability, a M2.4 at 10:53 pm Sunday, located 1 miles east of Panorama City. We haven't gotten any reports on this one, yet, but it could possibly have been felt.

This page is Last updated 17:59 PST March 31, 1999.