Below is a very simplified animation of transversal surface waves caused by an induced earthquake as result of (gas)exploration. This animation's solely goal is to help you understand the data in our graphs and should not be interpreted as scientific correct.
Earthquake NOT resulting in damage
In the the graph below in the middle of the domain there is a clear "V" visible in both plots. The top plot (X-axis) "V" is clearly bigger then the "V" in the bottom plot (Y-axis).
The "V" represents the moment in time the transversal wave passed below the building. Since both lines return to, and continue with, the exact same position and trend, no immediate damage is recorded.
Conclusion: The (part of the) wall where the sensor was mounted returned into the same position as before the earthquake. The movement in the X-direction of the sensor (top-plot) was much stronger then the movement in the Y-direction of the sensor. In the X-direction (parallel to the wall) the wall rotated, on average, 0.8x10-3 degrees.
The graph below shows the total arc (the difference between the highest measured value and the lowest measured value) during the passage of the quake.
Both spikes represent the maximal readings during the quake. This means the total rotation from "left to right"as the quake passes.
Conclusion: During the earthquake, in X-direction the wall rotated 0.02 degrees. And in Y-direction 0,025 degrees.
Below the Peak Ground Accelerations (PGA) in respectively X-, Y- and Z-direction. These measurements are te Peak Accelerations within sample periods from 5 seconds measured with a sample rate from 400Hz each channel.
Conclusion: During the, by gas exploration induced, earthquake the following Peak Ground Accelerations where recorded:
- In X - direction:0.24 m/s2
- In Y - direction:0.085 m/s2
- In Z - direction:0.34 m/s2
Given the local conditions, this was a relatively severe earthquake, that rotated and translated the wall in all directions. Based on these measurements no immediate damage was recored at the location of the sensor. Despite the recorded movements the wall returned to exactly the same position as before the earthquake. No plastic deformation is recorded. (Which does not mean it did not occur!)