Earthquake Commentary for July, 1999

Map of recent earthquake activity

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18:08 PDT, Thursday, July 29

We recorded and analysed 220 earthquakes in the past week. Click here to see a summary and map .

09:11 PDT, Wednesday, July 28

A M3.1 quake was felt last night at 10:38 pm. The quake was located 2 miles west of Devore, in the Cajon Pass area. This epicenter is in the San Jacinto fault zone, and the strike-slip focal mechanism is consistent with origin on that fault.

13:48 PDT, Saturday, July 24

Early this morning, at 2:43 am to be exact, there was another small quake that might possibly have been felt. It was a M2.5 Northridge aftershock, located 2 miles north-northeast of Granada Hills. We have not received any inquiries about it.

08:33 PDT, Saturday, July 24

Yesterday evening, there was a small swarm in the Imperial Valley, 1 mile south of El Centro. The largest events were: a M3.8 at 6:13 pm and a M3.7 at 7:01 pm. There were about a dozen smaller events also. The two large ones were felt in the Imperial Valley area, with at least one report from the San Diego area.

09:02 PDT, Friday, July 23

We recorded and analysed 218 earthquakes in the past week. Click here to see a summary and map .

06:04 PDT, Thursday, July 22

The quake that everyone felt in the Santa Clarita and northern San Fernando Valleys this morning was a M4.0 Northridge aftershock, located 4 miles west of Valencia. The time was 2:57 am. The focal mechanism was thrust. There have been a few "felt" reports from as far away as Hollywood.

15:55 PDT, Monday, July 19

At 3:09 pm today, the Anza/Hemet area experienced a M4.2 quake. The epicenter was 6 miles northwest of Anza, or 17 miles southwest of Palm Springs. This epicenter is in the complex San Jacinto Fault zone, and the preliminary focal mechanism suggests strike-slip consistent with that fault.

As fast as our data processing and pagers are getting to be, they still did not beat the "felt" calls from the public. This afternoon's quake was definitely felt from the Temecula area to the Palm Springs area.

11:48 PDT, Saturday, July 17

At 9:36 am today, there was a M3.0 located in the Mojave Desert 22 miles southeast of Goldstone Lake, or 26 miles northeast of Barstow. It is outside of the Landers aftershock zone. Due to the remote location, it was probably not felt.

16:12 PDT, Friday, July 16

There have been two quakes of interest today. The first was a M3.7 at 12:15 pm, located 6 miles east of San Nicolas Island. The second was a M3.4 at 3:51 pm, 21 miles west-southwest of Pt. Arguello (or 74 miles west of Santa Barbara). Both were offshore, and, as far as we know, neither was felt.

12:42 PDT, Friday, July 16

We recorded and analysed 240 earthquakes in the past week. Click here to see a summary and map .

17:42 PDT, Wednesday, July 14

The largest earthquake in the past day or so wasn't the one felt. The M3.2 located 5 southeast of Coso Junction went by completely unnoticed at 9:46 am this morning. The two that were felt were both Imperial county earthquakes: a M2.5 occurring last night at 6:43 and a M3.1 this morning at 12:57 am. Both earthquakes were located 5 miles south-southeast of Brawley.

15:44 PDT, Monday, July 12

Two more aftershocks from Sunday's M4.4 earthquake near Lake Isabella occurred this morning: a M3.0 at 7:36 am (PDT) and a M2.9 at 8:47 am. These too had the same location as the mainshock (see below). No report of them having been felt as of yet.

17:16 PDT, Sunday, July 11

At 3:16pm this afternoon there was a M3.4 earthquake 13 miles southwest of Ocotillo. There were no reports of it being felt.

16:57 PDT, Sunday, July 11

Sunday morning, at 11:20 am (PDT) the town of Lake Isabella was shaken by a M4.4 earthquake. Though presumably widely felt in the Lake Isabella area an earthquake this size (less than maginutude 5) is informally classified as "small". The M4.4 earthquake was followed roughly a minute and a half later by a M3.7 aftershock and then around 11:30 am (PDT) by a M3.4 aftershock. The mainshock and its aftershocks were all located 7 miles north of the town of Lake Isabella.

11:25 PDT, Friday, July 09

We recorded and analysed 172 earthquakes in the past week. Click here to see a summary and map .

10:16 PDT, Friday, July 09

Wednesday, the 7th, a M2.9 earthquake occurred 13 miles east-northeast of the city of Barstow. There were no reports of it being felt, but it was an aftershock to the M7.3 Landers mainshock which occurred just slightly over 7 years ago.

17:53 PDT, Thursday, July 01

We recorded and analysed 191 earthquakes in the past week. Click here to see a summary and map .

09:11 PDT, Thursday, July 01

At 5:43 am today, there was a M3.9 quake located close to the Garlock fault, 8 miles south-southeast of Tehachapi. The focal mechanism was mostly strike-slip, but with a somewhat more northerly strike that that of the Garlock fault. The quake was felt in the Tehachapi Mountains area.

This page is Last updated 18:08 PDT July 29, 1999.