Digital Diatribes

A presentation of data on climate and other stuff

Archive for the ‘Los Angeles’ Category

Los Angeles Earthquakes and Solar Cycles

Posted by The Diatribe Guy on January 25, 2009

Before I even start this post, I want to make it clear that I am not implying anything in particular about the correlation of earthquakes and solar cycles.  Secondly, I certainly am not making an implication about a specific geographical area’s earthquakes and solar cycles.

However, I read this article about a recent study on L.A. Earthquakes with some interest, and just decided to start poking around some solar cycle information, and I found what seems to be a somewhat interesting correlation.  I thought I’d throw it out here just for kicks.

First, let’s take the pertinent part of the article, as far as the study itself goes:

But the new research by UC Irvine scientists, to be published next week, found that major quakes occurred there roughly every 137 years over the last 700 years. Until now, scientists believed big quakes occurred along the fault roughly every 200 years.

Lisa Grant Ludwig, a principal investigator on the study, first visited the Carrizo Plain about 20 years ago, digging trenches in an area west of the Panorama Hills known as the Bidart Fan.

By looking at the pattern of soils and using radiocarbon dating on charcoal deposits, she found evidence of five large earthquakes dating back to the early 1200s. She found a gap of some 400 years between the 1857 earthquake and the one before, but only about 100 years separating the three preceding quakes.

Back then, the earthquake age estimates were very rough and the samples had to be fairly large, about the size of a jelly bean. Ludwig saved field notes and hundreds of soil samples in glass vials in her garage for more than 15 years, hoping that radiocarbon dating techniques would improve.

Once the technology improved, Ludwig and her colleagues could date samples with much higher precision and analyze charcoal flakes as small as the tip of a pencil.

They went back to her archive, and the redating effort, led by scholar Sinan Akciz, found that the four big earthquakes before the 1857 temblor probably occurred around 1310, 1393, 1585 and 1640.

Because they are looking at only a handful of earthquakes, scientists can’t be sure that the pattern will hold, Ludwig said.

Ludwig’s team has dug some new trenches in the area to supplement the redating project, hoping to find new soil samples that show the increased frequency of large earthquakes.

Results won’t be finalized for a few months, Ludwig said, but preliminary analysis suggests that the time interval between earthquakes may be even shorter, something on the order of 100 years.

My first reaction to this was, “You have 5 data points, totaling 4 time differentials, and two of those differentials are 192 years and 237 years. It’s kind of difficult to get too worked up about a simple average and say that things are overdue.”

But another part of me was intrigued in that we had actual dates. My initial reaction was to go to sunspot counts. Unfortunately, only one of those dates coincides with any remotely good monthly sunspot numbers.

I decided to head to a different source. Landscheidt’s Swinging Sun paper I’ve discussed from time to time.

One chart from this paper caught my attention. I have included it here, with the dates of the earthquakes as provided in the article superimposed on it with the red lines. I eyeballed it, but it’s close enough for jazz:


Some explanation is in order regarding the chart. I have included the verbiage from the paper regarding that exhibit (Figure 5 in the paper), with a couple explanatory notes to clarify things where necessary.

The plot in Fig. 5, the author of which is Gleissberg (1958), shows the secularly smoothed invervals DM between consecutive maxima in the 11 Year Cycle which also follow the 80 Year Cycle. Minima of DM correspond to maxima of the highest smoothed monthly average of sunspot numbers RM and vice versa. Gleissberg’splot covering the years AD 300 to 1950 is based on data published by Schove (1955) . [Layman’s terms: the shorter the cycle, the higher the magnitude on a monthly average basis.]
Secularly smoothed intervals DM between consecutive maxima in the 11-yr cycle contouring the secular variations in solar activity which are synchronous with relevant distance minima RDM meeting the time integral of torque criterion Cnl. Positive and negative RDM, the polarities of which follow the phases of the 79-yr cycle, are represented by arrows pointing up or down respectively. [Layman’s terms: The relevant Distance Minima means the distance of the center of the sun from the center of mass of the solar system. The chart shows a correlation between the distance of the center of sun from the center of mass of the solar system with cycle length.

The arrows in Fig. 5 represent the positive and negative RDM the dates and polarities of which are given in Fig. 4. [not shown – the up-arrows correspond with positive polarity. Polarity here is not referring to polarity of sunspots, but of the phase in the 79-year cycle.] Few successive RDM showing the same polarity at the short interval of about 20 years like —RDM 458, —RDM 481 or +RDM 816, +RDM 839 were marked at the mean date. The correspondence with peaks and troughs in the Gleissberg data is evident.

Well, I’m just throwing this out there. The earthquakes seem to correspond in their timing at some point after a relative distance minimum corresponding to short cycles with positive phase polarity, but before the next distance minimum corresponding to longer cycles with negative phase polarity.

Since there are only 5 dates presented, this could be coincidence. In addition, while the earthquakes coincided with that criteria, it is not the same as saying that criteria always corresponded with an earthquake.

Nonetheless, I thought it an interesting chart, be it coincidence or something more real than mere coincidence.

The current criteria according to the charts is currently satisfied. We are on the downside of a series of short cycles. The current cycle is longer. If the next cycle would be long as well, then the next few years represents a window where – if past correlation is more than coincidence – could represent a potential earthquake event for Los Angeles. This is far from conclusive, but interesting nonetheless.

We are currently on the area of the polarity phase that also matches the criteria. Based on past events, we would be on the right spot of the chart until 2020-2025.

Here’s hoping that this is pure coincidence.

Posted in California, Current Events, Cycles, Earth, Earthquakes, Landscheidt, Los Angeles, News, Science, Solar cycles, Sun, Sunspots | Tagged: , , , , | 4 Comments »