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Surface waves

• Rayleigh wave Love wave

A dispersed Rayleigh wave generated by an earthquake in Alabama near the Gulf coast, and recorded in Missouri.

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Solid lines marked P are compressional waves; dashed lines marked S are shear waves. S waves do not travel through the core but may be converted to compressional waves (marked K) on entering the core (PKP, SKS). Waves may be reflected at the surface (PP, PPP, SS).

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ANDRIJA MOHOROVIČIĆ(1857-1936)

• Andrija Mohorovičić was born in Volosko near Opatija. He attended secondary school in Rijeka and studied mathematics and physics at the Faculty of Philosophy in Prague in 1875. After graduating, he first taught in grammar school in Zagreb (1879-1880) and then secondary school in Osijek. On 1 November 1882 he began to teach at the Nautical School in Bakar, where he remained for 9 years. In 1891 he was transferred to the secondary school in Zagreb at his own request, and on 1 January 1892 he became the head of the Meteorological Observatory on Gric in Zagreb. …

• Work in the Nautical School in Bakar was crucial for the beginning of Andrija Mohorovicic's scientific work. This is where he first came into direct contact with meteorology, which he taught at the Nautical School, and which absorbed him to such a degree that he founded a meteorological station in Bakar in 1887…

• Analyzing the Pokuplje (Kupa Valley) earthquake of 8 October 1909, he advanced insight into the spreading of seismic waves …

The oceanic crust at the island of Hawaii is about 5 kilometers thick. The thickness of the continental crust under eastern California ranges from 25 kilometers under the Great Valley to 60 kilometers under the Sierra Nevada.

Seismographs

• "A body in motion tends to stay in motion unless acted upon by a force, and a body at rest tends to remain at rest unless acted upon by another force."

Classic seismogram

• Classic seismogram reads like a book. High- and low-gain instruments were recording separately.

Seismograph networks

• Digital record

Richter magnitudes

Magnitude = log10[Amplitude (mm)] + distance correction

Less than 3.5: recording only

3.5-5.4: often felt, rarely causes damage

Under 6.0: slight damage only

6-6.9: can be destructive across 100 km

7.0-7.9: major earthquake, serious damage

8 or more: great earthquake serius damage across 100’s km

The crust and mantle are plastic

• A heavy load on the crust, like an ice cap, large glacial lake, or mountain range, can bend the lithosphere down into the asthenosphere, which can flow out of the way. The load will sink until it is supported by buoyancy. If an ice cap melts or lake dries up due to climatic changes, or a mountain range erodes away, the lithosphere will buoyantly rise back up over thousands of years

Relative sea level rise for Fennoscandia in the 20th century derived from 70 very long-term tide-gauge records. The contours, measured in millimeters per year, roughly match the position and mass of the ice sheet that covered the region during the last glacial maximum.

Convection in the mantle

The red blobs are warmer plumes of less dense material, rising principally into the ocean-ridge spreading centers

R= 18O/16O, isto za HVoda-para: =Rvoda/Rpara

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Sediment-core records of the isotopic composition of biogenic calcite are available at various resolutions and record lengths covering the last 70 Ma. Though there are vital effects that modify the CaCO3-H2O fractionation, these are small.Problem: we have only the calcite, not the H2O from which it precipitated. So how much of the 18O variation is due directly to temperature (which controls fractionation between calcite and H2O) and how much due to the change in 18O of seawater?Why does seawater 18O change? Because of the growth and decay of ice sheets…But why is ice so light in 18O?