Is earthquake prediction possible?

Question

After the Tohoku and East Coast quakes, I skimmed over several books discussing the validity of earthquake prediction as a discipline, yet found no significant breakthroughs. What should change in our methods and models to enable timely forecasts to reduce casualties?

To be clearer, I am not interested in general assessment of seismic hazards (i.e. magnitude distribution for the next 25-50 years), but rather in short-term forecasts precise enough to order evacuation. I am aware that evacuation is a contentious issue...

Answer 1

Earthquake prediction really is a contentious issue, especially after the l'Aqula trials. However, let me try to elaborate how predictions might be possible in the future and what is inhibiting this development.

We do have some understanding of earthquakes and rupture mechanisms. However, for prediction in a scale of hours (sufficient for evacuation), we have to take the following into account. The stress fields in the crust are basically applying the pressure necessary for earthquakes. However, these are difficult to measure and different stresses may apply to the same region (local, regional, global stress fields). Just look at the world stress map below, how chaotic the different influences are.

Stress

These stresses are also pretty difficult to measure. These methods include (Source World Stress Map):

• Earthquake focal mechanisms
• Well bore breakouts and drilling-induced fractures
• In-situ stress measurements (overcoring, hydraulic fracturing, borehole slotter)
• Young geologic data (from fault-slip analysis and volcanic vent alignments)

These may sometimes give contradictory stress tensors. One of these reasons is that in-situ measurements are often more localized than focal mechanisms (as an example). But when we look at the map, we do have a lot of data (27.000 data points). Here another big problem comes into play:

Material

While geophysicists like to assume that the ground is homogeneous, it really isn't. A rupture may occur when the material at a fault fails under pressure. Yet the material is highly diverse and includes cracks and fractures that make it virtually impossible to make an accurate assessment. The material may act elastic, ductile or brittle and that may be location-dependent. From this you cannot say if a small rupture triggers a larger earthquake due to stress transfer or if it stays a small earthquake.

What would be to improve

This would make a simulation highly chaotic and the prediction would have a high probability to be false positive or false negative, therefore, decreasing the reliability significantly.

In the end we would have to improve our understanding of:

• Stress fields
• Stress-Strain relations
• Rupture mechanisms
• Material science and location

Early Warning in California

Nevertheless, an earthquake early warning (EEW) system is being implemented in California (and tested). It's called CISN ShakeAlert. They can use the trick that so-called P-waves of earthquakes are faster (and less destructive) than surface waves. This can give valuable time to safety-relevant systems like nuclear plants or high speed trains. But this is in a very early stage, when an earthquake already happened and is bound to arrive somewhere.

(I would have loved to put down more links, but my rep is too low, so see Wikipedia for Rupture Mechanics, Stress-Strain relations, the World Stress Map website and the CISN ShakeAlert website.)

Answer 2

You ask what we should change to better predict earthquakes, and I'd think almost everything. As geophysicists we might know the what of earthquake detonation, but are relatively blind at the how. There is a strong group of scientists who feel that single event prediction is NOT a realistic goal, and may perhaps be impossible.

Some good guesses as to why this is still a problem:

• Geophysicists still do not perfectly understand elastic rebound theory, as our earthquake simulations require assumptions that are not in line with the classical model.
• The equations governing earthquakes are most definitely non-linear, and the mathematical techniques that might describe earthquake motion and eruption might not even exist yet. An example of a situation like this is Knot Theory and DNA, where it was very difficult to mathematically represent DNA structures until Knot Theory came about (it is probably still difficult, but at least there is maths for it).
• The theory of plate tectonics, the overall cause of earthquakes, is not fully complete, and a mapping and characterization of its mantle flow is not understood.
• Modeling the effects of seismic anisotropy, most notably lattice preferred orientation, is not understood. Most notably, its role in mantle wedge dynamics.

But these are just guesses, and really, thats all we have. Shots in the dark.

Answer 3

Besides the theoretical limitations that @Neo talks about, there is also a great data gap in our knowledge. To predict an earthquake, we would need to know:

• The 3D geometry of all major, and possibly minor, fault zones
• The distribution of stress in the lithosphere, at least close to the fault zones but possibly more
• The physical characteristics of the rocks in faults (friction, brittleness, etc)

Our knowledge of the above is limited, at best. So to accurately predict earthquakes we'd need not only better equations, but also a lot more data.

Answer 4

See it is relatively easy to predict where a large earthquake might occur, assuming you have been monitoring deformation for a long enough period, more or less equal to the average inter-seismic interval (decades-centuries).

In principle earthquakes are simple, i.e., the fault accumulates strain and then eventually slips/ruptures. The million dollar question is what triggers it, and till date there has not been a single reliable precursor.

It is like predicting failure of a wooden (e.g., balsa) stick by bending the two sides with your hands, i.e., you know it will break more or less somewhere near the center, where the strain is highest (assuming homogeneity in properties and geometry) but getting the timing right is significantly harder and very difficult to reproduce. It is even harder in case of earthquakes, given the heterogeneity, non-linearity in the system.

So with time it will get easier to predict location of large earthquakes, as we monitor strain accumulation using modern tools like GPS, InSAR etc., but getting the timing right to even within a few years will be much harder. For example, we know that Southern San Andreas is due to for an earthquake (just based on the amount of slip deficit) as the last major earthquake was in 1857. But will this earthquake occur, today, in five years or within next 50 years, is unknown. Having said that additional faults in SoCal (e.g., San Jacinto and Elsinore) make the situation even more complex. Same goes for the North Anatolian fault near Istanbul, i.e., we know that an earthquake will occur there soon, as the entire plate boundary except the part near Istanbul had ruptured at least once in the last hundred years. See here for more details.

But getting the timing right for short term forecasts right now (and IMHO even in the next few decades) is impossible. Your only hope is alarms based on P-wave arrivals but then the earthquake has already started and heading towards you. Note: P waves arrive faster than surface waves, which cause most of the destruction so you might have a few seconds (depending on how far you are from the hypocenter) to take cover, automatically shutdown crucial stuff like gas flow in underground pipelines, subways, power plants etc.

Answer 5

One method of earthquake prediction that is being actively studied are radioactive radon isotope anomalies at the surface preceding an earthquake.

According to the article Radon as an Earthquake Precursor – Methods for Detecting Anomalies (Gregorič et al.), the radon isotope $\ce{^222Rn}$ originates from the radioactive decay of $\ce{^226Ra}$ as part of the $\ce{^238U}$ decay chain that occurs naturally in varying degrees in the Earth's crust. Due to the relatively short half-life of the $\ce{^222Rn}$ isotope.

Gregorič et al. explains that the altered stress-strain dynamics before an earthquake alters the transport of "geogas", which consists of carrier volatiles (e.g. $\ce{CO2}$, $\ce{CH4}$) and rarer gases within (including $\ce{Rn}$) via grounwater (liquid-phase advection), gas flow through cracks and fissures (gas-phase advection), or by quick 'bubble flow' via being carried on buoyant 'bubbles' through aquifers and water filled fractures.

Of course, this method is highly dependent on he amount of the amount of the radiogenic source already present, and factors such as soil grain size and meteorological parameters (e.g. soil moisture, rainfall, air pressure and temperature) can affect the concentrations of $\ce{^222Rn}$ at the surface, research is ongoing to determine the seismic source vs meteorological sources of radon emissions.

Observations presented in the paper Radon Monitoring in Soil Gas and Ground Water for Earthquake Prediction Studies in North West Himalayas, India (Singh et al. 2010) found some correlation between surface measurements of radon and he occurrences of earthquakes, but confirmed that these were significantly affected by meteorological events and also stated that monitoring of other carrier (and rare) gases is required to potentially more accurately predict an earthquake.

In a very recent paper, Detecting precursory patterns to enhance earthquake prediction in Chile (Florido et al. 2015) also state that in Chile, one of the recognised precursors are radon gas fluctuations occurring in the soil, groundwater and air.

Answer 6

As of Spring 2014, the Oklahoma Geological Survey and the USGS generated a press release (www.okgeosurvey1.gov/media/press/Full_USGS-OGS_Statment_05022014.pdf) warning of increased seismic activity in Oklahoma. The survey geologists observed an increase in both the occurrence and magnitude of earthquakes in the state, likely related to the increased occurrence of injecting waste water into the ground although some workers have attributed this increase to changes in lake levels.

In this case, geologists issued a warning of the potential for increased seismic activity based on the current observed trends of earthquake magnitude and occurrence. This warning assumes that whatever factor is causing this seismicity will continue (and potentially increase).

Answer 7

Although perfect forecasting of where and when the next earthquake will occur (which is how the public interprets the term 'prediction') is not physically impossible, this requires more information than we have at present. It is possible that in the future we could have enough understanding of earthquake mechanisms, and real-time knowledge of precursors, to actually forecast the next earthquake at least as precisely as we can currently forecast the next major flood or storm.

The interests of society are better served by the evaluation and mitigation of seismic hazards rather than by predicting earthquakes. A precise prediction of an earthquake might actually be less useful than an accurate evaluation of seismic hazards - if the objective is to minimize the loss of life and property.

Questions such as this one can be improved by deciding whether you are asking about seismic risk or the physical mechanisms of earthquakes. If the latter, you need to be more specific about what hypothesis you are asking about.

In fact, the basic physical mechanism responsible for earthquakes is understood to be elastic rebound . It's really the details of that mechanism that are still the subject of study.

If you are asking whether it will be possible, in the future, to forecast earthquakes sufficiently well to justify the evacuation of a major city, I would say yes. However, that is also going to depend upon municipal emergency evacuation capacity.

The prediction of an earthquake has consequences in and of itself, and seismologists have been: Sent to Jail for Being Too Flippant.

If I had to guess where the future breakthroughs in seismology leading to better earthquake forecasting will come from - I would guess real-time remote sensing of crustal deformation from space platforms. This will produce large amounts of data about fault-zones, in real-time and computer-accessible format, that can be interpreted in terms of our present understanding of earthquake physics.

Answer 8

While we have yet to produce a scientific method that reliably predicts earthquakes well in advance of their occurrence, anecdotal evidence suggests that animals can sense earthquakes before they happen. Kirschvink (2000) suggests that the 'sixth sense' in animals is an evolutionary mechanism coined the "seismic-escape response". While it is possible that some animals may be picking up on minor fluctuations in electromagnetic fields or foreshocks, there is little research to substantiate this. However, there are studies in progress, such as the International Cooperation for Animal Research Using Space that may help substantiate some claims. Stanley Coren has conducted some thought-provoking research with dogs that might point to predictive abilities.