Earthquake Commentary for January, 2002

Map of recent earthquake activity

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16:24 PST, Thursday, January 31

We have recorded and located 257 earthquakes in the last week. Click here to see a summary and map .

11:59 PST, Wednesday, January 30

Two more felt quakes occurred in the Simi Valley sequence late this morning: a M3.5 just before 10:48 am and a M3.0 just before 10:59 am. Both were felt, the first one as far away as Pasadena.

12:30 PST, Tuesday, January 29

At 12:20 pm and 12:27 pm today, two more aftershocks have occurred to last night's M4.2. The first had a magnitude of M3.6, and was felt in the northern San Fernando Valley. The second had a magnitude of M3.1.

12:11 PST, Tuesday, January 29

Another small Simi/Valencia quake has been felt, an aftershock of last night's M4.2. This one was a M2.7 at 11:20 am today, located 6 miles north-northeast of Simi Vallley. It was felt in Valencia, Simi Valley, and Canyon Country.

07:48 PST, Tuesday, January 29

There has been a M3.0 this morning, located offshore about 24 miles south of the east end of Santa Cruz Island. The time was 7:31 am. It is not expected that anyone will have felt this quake, due to its distance from shore.

07:26 PST, Tuesday, January 29

A series of quakes occurred last night to the northwest of San Fernando Valley. The largest ones were a M4.2 at 9:53 pm, a M3.9 at 10:00 pm, and a M3.8 at 10:08 pm. These were located about halfway between Simi Valley and Valencia. There have been 11 smaller aftershocks as well at this location.

All three of the largest quakes were felt fairly widely, the M4.2 as far away as Antelope Valley, the Grapevine area, and Orange County. The peak Modified Mercalli Intensity was IV. The M3.9 was felt as far as Ventura and Pasadena, and also had a peak Intensity of IV, over a smaller area.

The question of whether these quakes are Northridge aftershocks or not will certainly arise, and may not be so easy to answer. Technically, aftershocks continue at an ever decreasing rate until the number of quakes per week, month, or whatever is down to the level it was before the mainshock. For a quake the size of Northridge, that can be many years later. In fact, the Northridge sequence is still visible on current seismicity maps, so aftershocks are really still going on. These might be some of them. On the other hand, San Fernando Valley may be getting on with its seismic life, so to speak.

Oddly enough, in the past week, there has been a smattering of tiny quakes strewn over the San Fernando Valley. All these were less than M2.0, and so were not felt by residents. Normally, when we see such a scattered distribution, we expect to find the "quakes" are caused by wind or other extraneous noise, or telemetry problems. These quakes, however, are real and correctly located. Their appearance before the Simi Valley/Valencia activity is probably coincidence, but it's worth a note in the commentary.

16:17 PST, Thursday, January 24

We have recorded and located 192 earthquakes in the last week. Click here to see a summary and map .

07:07 PST, Wednesday, January 23

At 8:48 pm last night, a couple of very sensitive people felt a small quake in Beverly Hills. The magnitude was M1.8. (Note that the real-time computer systems initially located this quake in Studio City, which is wrong. With very small quakes, it is easy for the computers to be confused by seismic noise due to human activity, wind, noisy communications lines, etc.)

06:57 PST, Tuesday, January 22

A M3.3 quake occurred just after midnight this morning, at 12:39 am, 10 miles north-northwest of Fillmore. The quake was slightly felt in the Ventura, Ojai, Santa Paula and Castaic areas.

14:35 PST, Monday, January 21

Another M2.8 quake occurred this morning (Monday), 5 miles east-northeast of Ocotillo Wells. The time was 10:23 am. So far we have no reports of it being felt.

12:00 PST, Sunday, January 20

There was a small felt earthquake this morning, at 7:08 am, 13 miles northwest of Wrightwood. It was felt in the epicentral area.

08:59 PST, Friday, January 18

There was a M3.5 member of the Baja swarm overnight, at 1:23 am. The epicenter was located 32 miles southeast of Calexico. It might have been felt by people in the southern part of the Imperial Valley, but we have not received any reports yet that it was.

16:29 PST, Thursday, January 17

We have recorded and located 162 earthquakes in the last week. Click here to see a summary and map .

In case you've forgotten, today is the 8th anniversary of the Northridge quake, magnitude Mw6.7.

14:45 PST, Thursday, January 17

A number of people in the Orange County area reported feeling a quake yesterday (Wednesday) morning between 9:35 am and 9:40 am. The SCSN did not detect an earthquake at this time. However, the real-time system saves seven days of raw data, and, when I checked at this time range, I found a number of sonic signatures. So... the cause of the small seismic disturbance was probably loud airplanes and not the Earth.

16:28 PST, Thursday, January 10

We have recorded and located 360 earthquakes in the last week. Click here to see a summary and map .

07:01 PST, Thursday, January 10

Several small events have occurred in the past few days in the Imperial Valley, 7 miles east-northeast of Calexico. The largest ones have been: a M2.5 at 9:33 am yesterday, another M2.5 at 1:25 pm yesterday, a M2.9 at 3:39 am this morning, and a M2.8 at 3:51 am this morning. This region is at the intersection of the Imperial fault and the Brawley Seismic Zone, which is prone to earthquake swarms.

11:55 PST, Monday, January 07

It seems that there was another earthquake felt over the weekend. At 1:44 am on Saturday, a M2.0 occurred a mile north-northwest of Culver City. Surprisingly, it was felt at several locations in Culver City, Santa Monica, West Los Angeles, Westchester, and areas of Los Angeles.

08:48 PST, Monday, January 07

Note that there has been a sizable swarm in northern Baja over the weekend, the largest event being a M3.6 at 8:24 pm on Friday. This quake was located about 30 miles southeast of Calexico and was accompanied by a number of quakes in the lower M3's and the M2 range. The M3.6 was reported felt in the El Centro area.

Also, last night at 7:22 pm, there was a Landers aftershock, located 24 miles north of Yucca Valley. It had a magnitude of M3.1. This is a very sparsely populated region, so we do not expect "felt reports".

16:20 PST, Thursday, January 03

We have recorded and located 230 earthquakes in the last week. Click here to see a summary and map .

12:20 PST, Wednesday, January 02

The new year started off shaking, mainly in San Diego county. First with a M3.0 earthquake on January 1st at 1:23 pm near Ocotillo Wells, then with a kicker this morning with a M4.2 quake located 10 miles north-northwest of Borrego Springs at 4:11 am. This morning's quake was widely felt according to the "Did You Feel It?" statistics page. The fault plane solution for this event shows mainly strike-slip movement with some slight vertical movement. No damage is suspected from a quake of this size though it's a a nice reminder, especially for the new year, that earthquake damage is preventable with preparation.

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Last updated 16:24 PST January 31, 2002.