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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.





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


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


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.




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.




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



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

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