LIDAR remote sensing is a new approach for study geological structures with vertical accuracy 5-10 cm or better. Important that foliage that covers these structures can be removed by processing LIDAR data.
This part of the Puerto Rico coast shows a set of dunes which reflect, may be, a record of strongest Caribbean hurricanes. Top of the figure: color satellite photo shows the small village between the delta of the river and the ocean beach; bottom: LIDAR data, where buildings and most vegetation were removed by our processing, shows about a dozen of old dunes with a height ~1 m and a length ~100 m.
Earth and earthquakes:
Earthquakes often seem to strike without warning, sometimes inflicting massive damage and casualties. Accurate short term predictions of quakes are the goal of today's scientists. Many of the earthquakes are located in the areas where plates collide or try to slide past each other. Analysis of data on more than 125,000 earthquakes from the catalog of the National Earthquakes Information Center (USGS) throughout the world for period 1964-1990 shows remarkable phenomena [1-4]:
- the negative correlation in seismic activity at the boundaries of tectonic plates [1,4];
- the positive correlation between seismicity and the Earth’s rotation irregularity [2,3].
A phenomenon of negative correlation between different branches of subduction zones and systems of mid-ocean ridges and continental mountain ranges is typical for shallow (< 400km) and weak (M < 5) earthquakes. A mirror seismic component with characteristic times of about 3 years between two subduction zones – the Himalayas-Fiji and Philippines-Kamchatka (the total number of events is 60632) have the negative coefficient of correlation
Q = -0.74±0.09 (see the figure from ). Stronger (M > 5.4) or deeper (> 400km) earthquakes mostly demonstrate positive correlation in the same regions.
The correlation between the modulus of the Earth’s angular acceleration and global seismic activity is traceable in all types of seismically active regions: spreading zones (mid-ocean ridge system), subduction zones, strike slip zones of plates, regions of intraplate earthquakes, and the European segment of the Alpine-Himalayan orogenic belt [2,3]. For example, considering all earthquakes in the American-Mexican coast of the Pacific we find that this coefficient of correlation Q is at a maximum for two magnitudes:
Q = 0.68 +/- 0.10 for M>5.0 (438 events)
Q = 0.62 +/- 0.10 for M>5.4 (136 events)
Deeper earthquakes in the California show stronger positive correlation with the Earth rotation (see the figure from ).
1. Gorkavyi, N.N., Levitskii, L.S., Taidakova, T.A., Trapeznikov, Yu.A. and Fridman, A.M. 1999, On the Negative Seismic Activity Correlation between the Subduction Zones of the Pacific and Indian-Australian Plates and at the Mid-Ocean Ridge Intersection. Physics of the Solid Earth, Vol.35, No.11, p.906-916.
2. Gorkavyi, N.N., Levitskii, L.S., Taidakova, T.A., Trapeznikov, Yu.A. and Fridman, A.M. 1999, Correlation between Regional Seismicity and the Earth's Rotation Irregularity as a Function of the Earthquakes Sources Depth. Physics of the Solid Earth, Vol.35, No.10, p.840-853.
3. Gorkavyi, N.N., Levitskyi, L.S., Taidakova, T.A., Trapeznikov, Yu.A. and Fridman, A.M. 1995, The magnitude-dependent correlation of the Earth's angular speed and its acceleration with occurence frequency of earthquakes. Physics of the Solid Earth, Vol.30, No.10, p.884-889.
4. Gorkavyi, N.N., Levitskyi, L.S., Taidakova, T.A., Trapeznikov, Yu.A. and Fridman, A.M. 1995, Three components of seismic activity of the Earth. Physics of the Solid Earth, Vol.30, No.10, p.875-883.