One of the most powerful approaches for understanding the 3‐D thermo‐chemical structure of the lower mantle is to link tomographic models with mineral physics data. This is not straightforward because of strong trade‐offs between thermal and chemical structures and their influence on seismic structures. They can be reduced by mapping simultaneously perturbations of wave speeds and density anomalies and by the quantitative assessment of the accuracy and uniqueness of seismic and mineralogical data. Here, we present new tomographic maps of low order even‐degree seismic structures which are an improvement on earlier models. They satisfy constraints from body wave, surface wave and normal mode data simultaneously, thereby enhancing the spatial resolution. Furthermore, the seismic structure at a given location is represented by a probability density function (pdf) which takes into account the uncertainty and non‐uniqueness of the solution due to modeling and data restrictions. Following a robust statistical procedure, we fit heterogeneity of wave speeds and density from hypothetical thermo‐chemical models to those of our tomographic maps. We thereby constrain lateral variations of temperature as well as iron, silica and post‐perovskite concentration in terms of pdfs. Our work shows that large scale chemical variations are likely everywhere in the lower mantle. In most of the D″ region post‐perovskite is most abundant in the Circum‐Pacific belt, but near the core its lateral variation is more complex. Furthermore, post‐perovskite concentration trades off with the amplitudes of temperature and silicate variations, but not with their lateral distribution. This might be the reason why temperature and silicate variations appear not constrained by our data in the lowermost few hundred km of the mantle.

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In this study, we have evaluated the probabilistic and deterministic seismic hazard for the city of Almaty, the largest city in Kazakhstan, which has a population of nearly 2 million people.Almaty is located in the Tien Shan mountain belt, a low strain rate environment within the interior of the Eurasian plate that is characterized by large, infrequent earthquakes. A robust assessment of seismic hazard for Almaty is challenging because current knowledge about the occurrence of large earthquakes is limited due to the short duration of the earthquake catalogue and only partial information about the geometry, rupture behaviour, slip rate, and the maximum expected earthquake magnitude of the faults in the area. The impact that this incomplete knowledge has on assessing seismic hazard in this area can be overcome by using both probabilistic and deterministic approaches and integrating the results.First, we simulate ground shaking scenarios for three destructive historical earthquakes that occurred in the Northern Tien Shan in 1887, 1889 and 1911, using ground motion prediction 2 equations (GMPEs) and realistic fault rupture models based on recent geomorphological studies. We show that the large variability in the GMPEs results in large uncertainty in the ground motion simulations. Then, we estimate the seismic hazard probabilistically using a Monte Carlo-based PSHA and the earthquake catalogue compiled from the databases of the International Seismological Centre and the British Geological Survey. The results show that earthquakes of Mw 7.0 to 7.5 at Joyner-Boore distances of less than 10 km from the city pose a significant hazard to Almaty due to their proximity. These potential future earthquakes are similar to the 1887 Verny earthquake in terms of their magnitude and distance from Almaty.Unfortunately, this is the least well understood of the destructive historical earthquakes that have occurred in the Northern Tien Shan.

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