Author: Eric Bergman

Since I last posted about new calibrated clusters for GCCEL in April, I have uploaded 15 new ones, bringing the total number of calibrated clusters to 359. The regions I’ve been working in include the western U.S., Japan and China. You can see them at the “MLOC data for GCCEL” page .

mloc version 11 is a major update to the software that has been in progress since March of this year. I have done a considerable amount of testing and I’ve been using it for recent calibrated clusters uploaded to the GCCEL database. I’m no longer finding (m)any bugs with the way I typically use it, but several other people are using mloc for rather different studies however and they may well uncover a few more bugs that need attention. I expect to declare this version ready for release in the next month or two.

The main advantage of version 11 is the management of memory, which is much more efficient now. As a result the limitation that previously existed on the number of events that can be in a cluster has been lifted. I have made runs with clusters of over 500 events and one of the current users is running clusters approaching 1000 events. Of course, these runs still take a lot of time, and careful analysis of such large clusters is very time-consuming. The other main advantage of version 11 is not evident to the user, but very useful for the developer: placing all subroutines in Fortran modules and getting rid of large named common blocks in include files to handle global variables.

One known issue that I will try to resolve before release of v11 is the annoying discovery that the scripts it produces for plots are in some cases incompatible with GMT v6.5. For the time being, GMT 6.4 or below must be used.

As I’ve added more features to mloc over the years its memory requirements have grown to the point where we are now encountering problems on some systems when trying to run larger clusters. I won’t try to describe the details here but I’m happy to discuss it with you if you get in touch. In the old days it was referred to as “stack overflow” but modern chips and OSes have much more complex memory management systems and I don’t really know what is specifically failing. The original software structure, written in the 1980s is based mainly on Fortran 77 and relies heavily on include files and named common blocks that hit the stack very hard. The good news is that Fortran 90 (which is the standard used for mloc) has some features that should make it possible to substantially reduce the memory requirements for a given problem size, and thus make it feasible to run clusters with more events and/or arrival time data. I am now working on the next generation of the code that takes advantage of some of those features, in particular, modules and allocatable arrays. The reorganization should also make it easier to maintain and develop the code further. So for some period of time I will not be working on new calibrated clusters (much). I will post here when I have a version ready for testing.

The Salem cluster in northwest Oregon has been posted in the “mloc data for GCCEL” section.

A calibrated cluster in the Seattle, Washington area has been posted to GCCEL.

The distribution package for mloc v10.6.6, release date April 18, 2024, is now available on the Distribution page.

New calibrated clusters in Alaska (Nabesna) and Japan (Uwajima) have been uploaded, plus an update to the Califon, New Jersey cluster with data from a temporary network.

A calibrated cluster based on the recent Hualien 7.4 Mw sequence on the northeastern coast of Taiwan has been uploaded to the “mloc data for GCCEL” section.

The cluster is based on the 4.8 Mw earthquake that shook New York earlier today. The rest of the cluster consists of small events, mostly less than magnitude 3 and observed only within about 700 km.

I uploaded the Antofagasta cluster, named after Antofagasta, Chile. It includes the Mw 7.7 “Tocopilla” earthquake on November 14, 2007.