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The main difficulty in seismic full waveform inversion (FWI) is the strong nonlinearity, which is caused by the complexity of seismic wave propagation. Different components of elastic parameters result in different characteristics in seismic data. Meanwhile, different inversion quality is required in different stages of exploration or exploitation. So, there is no need to pursue matching all the seismic information during the inversion. Some problems can be solved by matching part of seismic information and the strong nonlinearity can also be avoided by this way. According to this consideration, a generalized FWI strategy and method based on seismic data subsets is presented. For different seismic data subsets, the gradients of the misfits have the same form and can be calculated by two times of seismic wave forward modeling just as traditional FWI. The only difference in calculating the gradients is the adjoint source. During the waveform inversion based on seismic data subsets, the responses of seismic data to different scales of perturbation on different media parameters should be analyzed intensively. Different seismic data subsets should be used in different stages of full waveform inversion. And then the residual of this seismic data subset is back-projected along the reasonable sub-kernels to decide where and which component of the model parameter need to be updated. As examples, envelope and reflection data subsets are used in FWI with synthetic and practical data to prove the validity and effectiveness of our presented FWI strategy and method. Especially, in the absence of low frequency contents, reasonable misfits can be used to recover the background compressional and shear velocity models using these FWI methods.

We propose a new waveform inversion method to improve the accuracy of the near surface velocity structure. Only the first-arrival waveform is used in this method to decrease the nonlinearity between wavefield and model parameters and the dependency of waveform inversion on the starting model. To increase the computational efficiency of forward calculation, we use Gaussian Beam (GB) method to calculate the Green function and the first-arrival wavefield. To avoid the storage of the huge Frechet matrix, based on Born wavepath, we propose the calculation of the direction and step length in waveform inversion using matrix decomposition, accomplished by accumulation. We then apply this new first-arrival waveform inversion method on a numerical experiment. The comparisons between this method and traditional acoustic full waveform inversion (FWI) and ray-based first-arrival traveltime tomography (RFTT) show that it can obtain a result a little worse than FWI while much better than traditional RFTT, while the computational efficiency is almost the same as RFTT. Meanwhile, the dependence of this method on the starting model is much weaker than FWI.

The main difficulty in seismic full-waveform inversion is the strong nonlinearity of these waveforms, which is caused by the complexity of seismic wave propagation. Analysis of objective-function behavior and its variations with the scale of parameter perturbations can help us to choose an appropriate inversion method and strategy. Using Jannane et al.'s method of analyzing objective-function behavior, we have studied the relationship between the objective functions calculated from different seismic data subsets and the scale of their parameter perturbations, especially their nonlinearity. These analytical results should provide some theoretical guidance for full-waveform inversion (FWI) to implement a multi-step and multi-scale inversion strategy.

Ultrafast dynamics of the first excited state (S-1) of chlorobenzene was studied using a combination of femtosecond time-resolved photoelectron imaging and time-resolved mass spectroscopy. One-photon absorption at 266.7 nm was used to populate the S-1 state of chlorobenzene. The time evolution of the parent ion signals consists of different biexponential decays. One is a fast component on a timescale of (152 +/- 3) fs and the other is a slow component with a timescale of (749 +/- 21) ps. Time-resolved electron kinetic energies (eKE) and time-resolved photoelectron angular distributions (PADs) were extracted from time-resolved photoelectron imaging and are discussed in detail. The ultrafast process with a time constant of (152 +/- 3) fs is a population transfer within the S-1 state, and only a vibrational energy transfer process with strong coupling is a reasonable explanation. This is attributed to an ultrafast process of dissipative intramolecular vibrational energy redistribution (IVR). The lifetime of the S-1 state was determined to be (749 +/- 21) ps, and its deactivation was due to slow internal conversion to the ground state. Additionally, nonadiabatic alignment and rotational dephasing of the S-1 state of chlorobenzene, as a typical asymmetric top molecule, were observed. The first C-type and J-type recurrences are expected at delay time of 205.8 and 359.3 ps, respectively.

Photodissociation dynamics of n-C5H11I at 266 and 277 nm was investigated using velocity map ion imaging. Speed and angular distributions of the corresponding photofragments were obtained by detecting ion images of I*(5p(2)P(1/2)) and I (5p(2)P(3/2)). Quantum yields of I* and I were also obtained. The contribution of parallel and perpendicular transitions and the relative fraction of each potential surface at different excitation wavelengths were determined. These determinations were based on the relative quantum yield and the angular distribution. It is found that a very strong nonadiabatic coupling exists between the two excited states (3)Q(0) and (1)Q(1), and the curve crossing probability rises gradually with a decrease in the excitation wavelength. Additionally, analysis of the angular distributions for the I* channel and the I channel at the same excitation wavelength revealed that the population of (3)Q(0) was the main pathway following excitation. However, when compared to the situation that the I* channel mainly results from the direct dissociation of the (3)Q(0) state, the I channel originates mostly from the nonadiabatic coupling between (3)Q(0) and (1)Q(1).

While the high-temperature exhumation process in the Dabie Mountain has been well documented, the low-temperature exhumation of this area since Cretaceous, especially since Late Cretaceous, is relatively less studied. Low-temperature thermochronology provides one of the important approaches to solve this problem. Based on the data of fission track and (U-Th)/He analysis of apaptites and zircons from the granitoid and metamorphic rocks in the Dabie Mountain, this paper applies Mancktelow’s and Braun’s methods to estimating the exhumation rates and to drawing the regional differential exhumation pattern since Cretaceous, especially since Late Cretaceous by taking into consideration factors such as heat transport, heat advection, topography and heat production, which could influence geothermal field in the shallow crust. Since Cretaceous, the exhumation rate (0.08－0.10 km/Ma) in the region around Tiantangzhai and in the south of Tanlu fault zone is larger than the rate (0.04－0.07 km/Ma) in other areas of the Dabie Mountain. The regional differential exhumation pattern might be related to the push-up effect caused by differential strike-slip movement along NNE-trending faults.