Over the past several years, interest in earthquake foreshocks has experienced considerable growth. This can, on one side, be explained by a largely improved observational database that spans all seismic scales. A development that is driven by a growing number of permanent seismic stations and large-scale campaign networks, the development of advanced detection and analysis techniques, and by the improvement of laboratory equipment and techniques. In addition, the ongoing endeavor to better understand induced seismicity has been contributing to this upgrowth with densely-monitored underground lab-scale experiments and enhanced microseismic monitoring. On the other side, earthquake foreshocks are widely perceived as one of the few and, as of now, most direct observations of earthquake nucleation processes.

Foreshocks are generally thought to arise by one of two mechanisms: cascading failure or preslip. The cascading model proposes that a mainshock following a foreshock has an identical origin to that of aftershocks. In this case, earthquake frequency-magnitude statistics predict that occasionally an aftershock will be larger than the prior event, which makes the prior event a foreshock only after the fact. The mechanism proposed by the preslip model is that premonitory processes - perhaps fault creep related to mainshock nucleation - result in stress changes that drive the foreshock process. Seismologists have found no agreement so far; this is made more difficult by two facts: that no agreed-upon, universal strategy to identify foreshocks in a seismic catalog exists and that data quality and quantity vary considerably over spatial and temporal scales.

In this session, we want to bring together scientists from all disciplines working on, or interested in, earthquake foreshock occurrence. We invite reports on observational and theoretical studies on all scales. This includes laboratory and deep underground experimental earthquakes, as well as microseismic to megathrust earthquakes. We also encourage submissions from colleagues working on advanced detection and analysis techniques for improved foreshock identification.

Co-organized as NP4.9/TS5.9
Convener: Toni Kraft | Co-conveners: Christine J Ruhl, Aitaro Kato
| Attendance Mon, 08 Apr, 16:15–18:00
Hall X2

Attendance time: Monday, 8 April 2019, 16:15–18:00 | Hall X2

Chairperson: Toni Kraft
X2.325 |
Lun-Kai Kang, Ruey-Juin Rau, and Ling-Hua Wang
X2.326 |
| Highlight
Samson Marty, Alexandre Schubnel, Blandine Gardonio, Harsha Bhat, Jérôme Aubry, Eiichi Fukuyama, and Raul Madariaga
X2.327 |
Roseanne Clement, Ian Main, and Andrew Bell
X2.328 |
Verena Simon, Toni Kraft, Tobias Diehl, and Stefan Wiemer
X2.329 |
Aitaro Kato and Toshihiro Igarashi
X2.330 |
Takahiro Hatano and Subhadeep Roy
X2.331 |
| solicited
| Highlight
Percy Eliel Gálvez Barrón, Paul Selvadurai, Ben Edwards, Thessa Tormann, Stefan Wiemer, and Steven Glaser
X2.332 |
Tomáš Fischer, Martin Bachura, Jana Doubravová, and Josef Horálek