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Water Resources - With conventional monitoring at low-frequency, biological responses to weather-related events are missed. In this paper, we examine the chlorophyll-a concentrations in a shallow...  相似文献   
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In October and November 2002, the Molise region (southern Italy) was struck by two moderate magnitude earthquakes within 24 hours followed by an one month long aftershocks sequence. Soon after the first mainshock (October 31st, 10.32 UTC, Mw 5.7), we deployed a temporary network of 35 three-component seismic stations. At the time of occurrence of the second main event (November 1st, 15.08 UTC, Mw 5.7) the eight local stations already installed allowed us to well constrain the hypocentral parameters. We present the location of the two mainshocks and 1929 aftershocks with 2 < ML < 4.2. Earthquake distribution reveals a E-trending 15 km long fault system composed by two main segments ruptured by the two mainshocks. Aftershocks define two sub-vertical dextral strike-slip fault segments in agreement with the mainshock fault plane solutions. P- and T-axes retrieved from 170 aftershocks focal mechanisms show a coherent kinematics: with a sub-horizontal NW and NE-trending P and T-axes, respectively. For a small percentage of focal mechanisms (∼ 10%) a rotation of T axes is observed, resulting in thrust solutions. The Apenninic active normal fault belt is located about 80 km westward of the 2002 epicentral area and significant seismicity occurs only 20-50 km to the east, in the Gargano promontory. Seismic hazard was thought to be small for this region because neither historical earthquake are reported in the Italian seismic catalogue or active faults were previously identified. In this context, the 2002 seismic sequence highlights the existence of trans-pressional active tectonics in between the extensional Apenninic belt and the Apulian foreland.  相似文献   
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Complexity–entropy causality plane (CECP) is a diagnostic diagram plotting normalized Shannon entropy \({\cal H}_S\) versus Jensen–Shannon complexity \({\cal C}_{JS}\) that has been introduced in nonlinear dynamics analysis to classify signals according to their degrees of randomness and complexity. In this study, we explore the applicability of CECP in hydrological studies by analyzing 80 daily stream flow time series recorded in the continental United States during a period of 75 years, surrogate sequences simulated by autoregressive models (with independent or long-range memory innovations), Theiler amplitude adjusted Fourier transform and Theiler phase randomization, and a set of signals drawn from nonlinear dynamic systems. The effect of seasonality, and the relationships between the CECP quantifiers and several physical and statistical properties of the observed time series are also studied. The results point out that: (1) the CECP can discriminate chaotic and stochastic signals in presence of moderate observational noise; (2) the signal classification depends on the sampling frequency and aggregation time scales; (3) both chaotic and stochastic systems can be compatible with the daily stream flow dynamics, when the focus is on the information content, thus setting these results in the context of the debate on observational equivalence; (4) the empirical relationships between \({\mathcal H}_S\) and \({\mathcal C}_{JS}\) and Hurst parameter H, base flow index, basin drainage area and stream flow quantiles highlight that the CECP quantifiers can be considered as proxies of the long-term low-frequency groundwater processes rather than proxies of the short-term high-frequency surface processes; (6) the joint application of linear and nonlinear diagnostics allows for a more comprehensive characterization of the stream flow time series.  相似文献   
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