11:00 〜 13:00
[PPS04-P08] The Seismicity of Mars as Recorded by InSight Marsquake Servise after 1100 sols
キーワード：火星、地震学、惑星探査
Since the successful landing of the NASA InSight lander, the Seismic Experiment for Interior Structure (SEIS) has realized a quasi-continuous monitoring of Martian seismicity for more than 1100 Martian sols, which is the InSight’s Martian day number . The Marsquake Service (MQS) is responsible for closely examining the continuous data flow from the red planet to identify seismic events hidden in the data. Today, the MQS Martian seismicity catalog includes almost 1000 distant marsquakes and more than 1000 high frequency signals, which are likely to be associated with thermal cracking on the Martian surface. We review here the MQS activity and report recent updates on the latest marsquake catalog.
The MQS is a team of well-trained seismologists that regularly investigate the seismic data that is down-linked from Mars. Continuous data from SEIS is down-linked a couple of times a day and we assign at least two seismologists to examine the data in a timely manner for the first inspection of the data. All the suspicious signals found in the data are reported to the team and go through a further review with wider members of the MQS where we finalize our event identification. Each event is given a name, a quality, arrival time picks and a location, if the quality permits. The event name is defined with the Martian sol of the detection and an alphabetical index to distinguish multiple events within a single sol (e.g. S0235b, which corresponds to the second event on Sol 235). We assign an event quality from A to D, with A being the highest, depending on the constraints we have on the locations. While quality A events have a well constrained location with a distance and a back azimuth, quality D events have no phase picks nor a location.
An interesting finding from MQS activities is that we found different types of marsquakes which show significantly distinct characteristics. These event types are discriminated based on their spectral content and we now have 6 separate types. These event types are also assigned during the MQS review process.
Low Frequency (LF): The energy is below the 2.4 Hz resonance, and most of the time is below 1 Hz.
Broadband (BB): Predominantly low frequency, but can include energy at and above the 2.4 Hz resonance.
High Frequency (HF): The energy is predominantly at 2.4 Hz but also includes energy above 4Hz. Some leakage of energy into low frequency is possible but the energy peak is at high frequency.
2.4 Hz: Narrow frequency excitation around 2.4 Hz. The energy reaches up to 4 Hz maximum. This type of event is likely to be a low amplitude version of High Frequency type event.
Very High Frequency (VF): The energy is at high frequency which can sometimes reach over 10 Hz, which is the Nyquist frequency of the continuous data stream. These events have clear enhancement of horizontal energy at high frequencies.
Super High Frequency (SF): In contrast to the other events that have durations of many minutes, these are very short duration (~10 s of seconds) events that have mainly horizontal energy at 5-10 Hz. Given the clear correlation with temperature variation, they are likely thermal cracks observed at near surface region.
All this information is then summarized in the MQS catalog which is released every three months, with a three months delay, simultaneously with the publication of the SEIS data. The latest version is the V9, which was released in January 2022. The catalog is released in a Quake ML format, which contains all the information in xml format. While the power situation of InSight is degrading, SEIS continues its observations. MQS will also continue to investigate the Martian seismicity and to create and curate the seismicity catalogue for Mars.
The MQS is a team of well-trained seismologists that regularly investigate the seismic data that is down-linked from Mars. Continuous data from SEIS is down-linked a couple of times a day and we assign at least two seismologists to examine the data in a timely manner for the first inspection of the data. All the suspicious signals found in the data are reported to the team and go through a further review with wider members of the MQS where we finalize our event identification. Each event is given a name, a quality, arrival time picks and a location, if the quality permits. The event name is defined with the Martian sol of the detection and an alphabetical index to distinguish multiple events within a single sol (e.g. S0235b, which corresponds to the second event on Sol 235). We assign an event quality from A to D, with A being the highest, depending on the constraints we have on the locations. While quality A events have a well constrained location with a distance and a back azimuth, quality D events have no phase picks nor a location.
An interesting finding from MQS activities is that we found different types of marsquakes which show significantly distinct characteristics. These event types are discriminated based on their spectral content and we now have 6 separate types. These event types are also assigned during the MQS review process.
Low Frequency (LF): The energy is below the 2.4 Hz resonance, and most of the time is below 1 Hz.
Broadband (BB): Predominantly low frequency, but can include energy at and above the 2.4 Hz resonance.
High Frequency (HF): The energy is predominantly at 2.4 Hz but also includes energy above 4Hz. Some leakage of energy into low frequency is possible but the energy peak is at high frequency.
2.4 Hz: Narrow frequency excitation around 2.4 Hz. The energy reaches up to 4 Hz maximum. This type of event is likely to be a low amplitude version of High Frequency type event.
Very High Frequency (VF): The energy is at high frequency which can sometimes reach over 10 Hz, which is the Nyquist frequency of the continuous data stream. These events have clear enhancement of horizontal energy at high frequencies.
Super High Frequency (SF): In contrast to the other events that have durations of many minutes, these are very short duration (~10 s of seconds) events that have mainly horizontal energy at 5-10 Hz. Given the clear correlation with temperature variation, they are likely thermal cracks observed at near surface region.
All this information is then summarized in the MQS catalog which is released every three months, with a three months delay, simultaneously with the publication of the SEIS data. The latest version is the V9, which was released in January 2022. The catalog is released in a Quake ML format, which contains all the information in xml format. While the power situation of InSight is degrading, SEIS continues its observations. MQS will also continue to investigate the Martian seismicity and to create and curate the seismicity catalogue for Mars.