BIG ONE COMING ?

On July 4 morning, a mild earthquake measuring 4.0 rocked CA at about 10 AM.

Personally I didnt experienced it and came to know about it only when another earthquake measuring 6.6 hit.

Since moving to CA, it isnt my first earthquake. I experienced few before. 

Just like before, googled to see whats going, enjoyed fun in Twitter and continued with my day as usual.

Next day evening,  I experienced something bigger. 

This one is different from previous ones. It keeps shacking for a while. By 9 PM PT, it's subdued but a ton of questions racing through my mind.. 

• Its night time and we will be in middle of sleep. Will it be safe going in ? 
• This one is differently bigger than yesterday. Will the next one going to be bigger ? If yes, how soon ?

I started searching for answers, but all i can see is "WELCOME TO CA" messages.

I am not new to CA and living here for a while. This isn't felt normal.

So I started searching for info on Earthquakes and found a treasure trove on USGS website. Analyzing its data, gave some insights..

Here you go!!

This is not normal. 

Number of earthquake measuring more than 2.5 magnitude this year already surpassed last 15 years.

More than half of all earthquakes so far this year happened on July 6th itself.
We had more number of earthquakes on July 6th than the last 2 years

Since 1900, This is the 4th highest earthquake recorded in CA and biggest in 20 years.

*1906 earthquake was excluded due to lack of sufficient data.

Since its confirmed not normal, I started to figure out whether it is safe or not. 

• Will 7.1 is going to be highest or Big one coming ?
• Does Before shocks relieve pressure and reduced possibility of a bigger magnitude quake ?

For this I examined the, other 3 highest earthquakes in CA history and trying to understand magnitude vs number of quakes.

1952 - July 21st 11 AM UTC (4 AM PT) - M7.5 

Before hitting max magnitude of 7.5, there wasn't any abnormal activity. But after hitting the max of 7.5, number of earthquakes with magnitude 6 increased.

Note: 7.5 Magnitude is rounded to 8 and showing as 8 in the graph but its 7.5 only.

1992 Jun 28th 11 AM UTC ( 4 AM PT) - 7.3 M

Here we can see that, there is a M6 few months before the major M7.3. After hitting max magnitude , there arent more 7s but 6s do happened after couple of months.

On activity front, This was a sudden earthquake hitting 7.3 and on the same day, not many aftershocks. But next day it picked up with 3s and 4s.

1999 Oct 16th 9 AM UTC ( 2 AM PT) - M7.1

In 1999 too, we had earthquakes measuring M6 before hitting a M7.1 couple of months later.

Be it a M6 or M7 . Most of the activity we are seeing is after the big quake hitting us, not before.

2019 July 6th 3AM UTC ( 8 PM PT) - M7.1

Like its predecessors, here too we had a quake measuring M6 before hitting a M7.

From activity standpoint, neither M6 nor M7 warned us with any increase in lower magnitude of earthquake activity.

so we can fairly say "smaller quakes relieving pressure and avoiding a bigger quake is a myth or at least not proven based on observations"

During this we do see a M6 followed by a M7. So I started looking at all earthquakes of magnitude M6.

Below you can see earthquakes M6 are more frequent than M7 and a M7 isnt always warned by a M6 as in 1999.

While earthquakes measuring M2, M3, M4 are more frequent, the moment we start seeing M5, M6, its better start pay attention and be extra cautious.

But this doesnt answer whether Big one coming or not.

so I started looking for experts in the area and found Lucy Jones, a PHD in Geophysics from MIT.

her on going work on earthquake is very impressive.

In fact, she warned upcoming earthquake a day before on July 3rd.

If the daily probability of the Big One was 50/50, then the chance it would happen in the next week would be >99%. Real probability is about 2% per yer, or 1/20,000 each day. Your change of being in a car accident today is ~1/7,000. I still wear my seat belt every day. https://t.co/3ovnAfiPFV

— Dr. Lucy Jones (@DrLucyJones) July 3, 2019

Continuing further, She initially felt M4.2 is foreshock to M6.6

A M6.6 near Ridgecrest. The M4.2 a half hour before was a foreshock. This area had lots of M5+s in the 198os. More soon

— Dr. Lucy Jones (@DrLucyJones) July 4, 2019

Later to her surprise, found M6.4 is foreshock to M7.1

So the M6.4 was a foreshock. This was a M7.1 on the same fault as has been producing the Searles Valley sequence. This is part of the same sequence -

— Dr. Lucy Jones (@DrLucyJones) July 6, 2019

It tell us that this area of science like many others is evolving. We are at a stage, we can predict something going to happen but not how bad or when.


She pointed out the two faults involved and its not the feared San Andreas fault.
There is a 10% chance of something bigger might happen. Remember that's also a 90% chance M7.1 is the largest.

The aftershocks to the #SearlesValley earthquake show that two faults are involved. One strikes northwest and the other northeast. You can see the aftershocks at https://t.co/BwTOi7AGG2 pic.twitter.com/gkDzPh4I9G

— Dr. Lucy Jones (@DrLucyJones) July 4, 2019

Yes, we estimate that there's about a 1 in 10 chance that Searles Valley will see another M7. That is a 9 in 10 chance that tonight's M7.1 was the largest.

— Dr. Lucy Jones (@DrLucyJones) July 6, 2019

Inline with what I identified in my study, she says there is no sure way to say if the next one going to be bigger or not. After a major quake, aftershock activity may go down but not the magnitude
But we do know when things arent normal.

What is happening now, isnt normal. So be prepared and cautious.

The number of aftershocks goes down with time, but not the magnitudes! The ratio of large to small quakes is constant. The big ones just become much less frequent. Large, late aftershocks show up in most sequences. The last M5 aftershock to 1994 Northridge was in 1997

— Dr. Lucy Jones (@DrLucyJones) July 7, 2019

If you want to know more, Lucy conducting a Q&A. Feel free to join

I’m conducting a Q&A 7/7 at 3pm PDT on @Stratiscope. Please direct questions to @stratiscope using #StratiscopeExpert, and I will answer as many questions as I can while I’m there.

— Dr. Lucy Jones (@DrLucyJones) July 7, 2019

Conclusions

1. What is happening now is NOT normal. we are seeing highest number of earthquakes in 15 years after 4th largest recorded earthquake in CA history.
2. Typically big earthquakes hits all of a sudden, with out any warning
3. After a major earthquake of M6 or greater, prepare for aftershocks. 
4. Current science evolution is at a point, where we can predict but cant guarantee date, time, location and intensity of an earth quake.
5. Follow @DrLucyJones on twitter to get educated