Sharpness of the mantle discontinuities

Abstract

Seismic estimates of sharpness of the mantle discontinuities are important for constraining models of composition and temperature in the deep Earth but these data are difficult to obtain. We explore a possibility to determine sharpness of the major mantle discontinuities (those at depths around 400 and 650 km) from the broad‐band records of phases converted from P to S underneath the receiver. Our estimates are obtained from a comparative analysis of waveforms of the converted phases and those of the P waves in the teleseismic records of BRV (Kazakhstan), GRF (Germany), NRE0 (Norway) and YKW (Canada). The data indicate that the shape of the pulse converted at the 400‐km discontinuity is close to that of the P wave whereas the pulse of the 650‐km conversion is substantially broader. We infer from this comparison that the 400‐km discontinuity is sharp (width of the transition zone is less than 5–7 km). The 650‐km transition is modelled by a linear gradient zone 20–30 km thick.

Deep Earth Structure - Transition Zone and Mantle Discontinuities

“…Petersen et al (1993b) found a sharper 410 (5-7 km) than 660 (20-30 km) from Ps conversions at several broadband stations in different regions. They observed that both discontinuities (410 and 660) were < 4 km sharp.…”

Oscillations of theBe7solar neutrinos inside the Earth

“…The modulations originate from the density jumps at distances h 1 = 410 km (by 5%) and at h 2 = 660 km (by 10%) from the surface of the Earth. These density changes occur over depth interval less than 5 km [19], [20], which is much smaller than the oscillation length. Therefore the jumps break adiabaticity.…”

Coherent Laser Control of the Product Distribution Obtained in the Photoexcitation of HI

“…2 (right). Potentla energy d~agraln for HI and I. obtaned from (15)(16)(17)(18). The short and long arrows on the eft ~ndicate the lnechanisln for-controlling the exc~tat~on of HI.…”

“…Figure 1 shows the three-photon photoionization spectrum obtained with the U V beam. The rotational structure in the HIsignal results from 2+ 1 resonance-enhanced multiphoton ionization (REMPI) of the b3112 and b3111 Rydberg states (15). The b 3 n l state is strongly predissociated and produces I atoms that are responsible for the peak seen in the Ispectrum near 351.8 nm.…”