Large earthquakes have semi-periodic behavior as a result of critically self-organized processes of stress accumulation and release in seismogenic regions. Hence, large earthquakes in a given region constitute semi-periodic sequences with recurrence times varying slightly from periodicity. In previous papers, it has been shown that it is possible to identify these sequences through Fourier analysis of the occurrence time series of large earthquakes from a given region, by realizing that not all earthquakes in the region need belong to the same sequence, since there can be more than one process of stress accumulation and release in the region. Sequence identification can be used to forecast earthquake occurrence with well determined confidence bounds. This paper presents improvements on the above mentioned sequence identification and forecasting method: the influence of earthquake size on the spectral analysis, and its importance in semi-periodic events identification are considered, which means that earthquake occurrence times are treated as a labeled point process; a revised estimation of nonrandomness probability is used; a better estimation of appropriate upper limit uncertainties to use in forecasts is introduced; and the use of Bayesian analysis to evaluate the posterior forecast performance is applied. This improved method was successfully tested on synthetic data and subsequently applied to real data from some specific regions. As an example of application, we show the analysis of data from the northeastern Japan Arc region, in which one semi-periodic sequence of four earthquakes with M C 8.0, having high non-randomness probability was identified. We compare the results of this analysis with those of the unlabeled point process analysis.

The polarity of first P-wave arrivals plays a significant role in the effective determination of focal mechanisms specially for smaller earthquakes. Manual estimation of polarities is not only time-consuming but also prone to human errors. This warrants a need for an automated algorithm for first motion polarity determination. We present a deep learning model -PolarCAP that uses an autoencoder architecture to identify first-motion polarities of earth-quake waveforms. PolarCAP is trained in a supervised fashion using more than 130,000 labelled traces from the Italian seismic dataset (INSTANCE) and is cross-validated on 22,000 traces to choose the most optimal set of hyperparameters. We obtain an accuracy of 0.98 on a completely unseen test dataset of almost 33,000 traces. Furthermore, we check the model generalizability by testing it on the datasets provided by previous works and show that our model achieves a higher recall on both positive and negative polarities.

<p>The Municipality of Zapopan, Jalisco, is located west of the Guadalajara Metropolitan Zone at the intersection of three rift zones: Tepic-Zacoalco, Chapala-Tula, and Colima. The importance of this region lies in the recent population growth that it has experienced in a few years. This growth has been supported by the development in commercial and service activities, and mainly in industry and technology, being ranked as the second-most populous city in Mexico, behind the federal capital.</p><p>The western region of the Guadalajara Metropolitan Zone (GMZ) has numerous fault systems where, historically, there have been significant earthquakes and seismic swarms such as those that occurred in 1685-1687, 1875, 1932, 1995 and 2002, showing similar characteristics. Besides, it is in this region where the Caldera de la Primavera is located, a rhyolitic volcanic caldera that continues presenting seismic and geothermal activity.</p><p>Recently, in the years 2015 and 2016, new seismic swarms occurred and were recorded instrumentally for the first time by the Jalisco Seismic and Accelerometric Network (RESAJ). The two seismic sequences took place in two alignments in the same direction as the Colima rift. These epicenters suggest the existence of two almost parallel normal faults, and that would be forming the Graben of Zapopan. Due to the length of these faults, 16 km for the east fault, and 28 km for the west fault, earthquakes of magnitudes 6.2 - 6.5 could be generated.</p><p>In the framework of the CeMIEGeo P-24 project (SENER-CONACyT), we continue studying the seismicity of this region with the deployment of 25 seismic stations in the vicinity of La Caldera de la Primavera. This study revealed the high seismicity that was taking place in the area of ​​Zapopan, Tesistán Valley, and La Caldera de la Primavera.</p><p>Based on these new studies and the knowledge of the seismic history of the region, a collaboration agreement has been established between the Research Group UDG-CA-276 SisVOc and Civil Protection of the Municipality of Zapopan for the installation of a local seismic network that will allow to define tectonic and structurally the fault systems of the region and mitigate the possible effects of the local seismicity in the population. Since May 2019, three Obsidian 8X seismic stations with Lennartz 1Hz LE3D and Episensor sensors and two accelerometers installed in the city have been operating, constituting the Zapopan Seismic and Accelerometric Network (RESAZ). The RESAZ operates together with the nearest stations of the RESAJ. In this work, we present the first results of the seismicity analysis recorded in Zapopan.</p>

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Numerous microearthquakes, ML ≤ 3.8, corresponding to background seismicity and swarms were observed from September 3, 2017, to January 1, 2018, mainly in the Tesistán Valley, north of the Guadalajara Metropolitan Zone (GMZ). We located 188 tectonic microearthquakes and identified 11 clusters of similar events from a spatio-temporal analysis and waveform cross-correlations. Our results confirm the presence of continuous seismicity in the GMZ that long went unobserved. Most M L ≥ 2.5 events and some clustered events are located in the northeastern Tesistán, close to the NNE-SSW fault corresponding to the eastern edge of the Zapopan Graben, a structure evidenced by 2015–2016 seismicity. Seismicity recorded during 2020 by a recent local seismic network installed in Zapopan reaffirms that frequent microseismicity is related to active faults that cross the cities of Zapopan and Guadalajara. The microseismicity distribution suggests minor faults with the same orientation and sense of displacement as the main structures bounding the Zapopan Graben, which corresponds to structures known as synthetic faults. This arrangement is common within the Basin and Range tectonic province. The seismicity in the northeast boundary of Jalisco Block is closely related to faults formed by Cenozoic deformation events that might be reactivated due to modern crustal dynamics. Active faults and the possibility of synthetic structures are a hypothesis that necessitates long-term seismic monitoring in order to assess the seismic hazard in the GMZ, which is a crucial factor for urban planning.