# Presentation: 524830

## Recent Reanalysisof the Apollo Lunar Seismic DataandRemaining ProblemsYosio Nakamura Institute for GeophysicsJohn A. & Katherine G. Jackson School of GeosciencesUniversity of Texas at AustinGoddard Space Flight Center Seminar, November 15, 2007

## Outline

-   Brief history of Apollo Passive Seismic Experiment
-   More reliable estimates of seismic velocity distribution
-   A new look at deep moonquakes
-   What causes shallow moonquakes?
-   Remaining problems

## Apollo 11 EASEP being setup by an astronaut July 1969

- Problems Facing us in Future Missions

- Apollo 11 EASEP being setup by an astronaut July 1969

## Slide 4

## Sample Apollo 11 EASEP Seismograms

## Apollo 16 Seismometer Deployed on the MoonApril 1972

**Apollo 16 Seismometer Deployed on ****the Moon****April 1972**

## Apollo Landing Sites

| Apollo Station | Passive Seismic Experiment | Other ‘Seismic’ Experiments |
| --- | --- | --- |
| 11 | 7/21/1969 –/8/271969 |  |
| 12 | 11/19/1969–9/30/1977 |  |
| 14 | 2/5/1971 –9/30/1977 | ASE |
| 15 | 7/31/1971 –9/30/1977 |  |
| 16 | 4/21/1972 –9/30/1977 | ASE |
| 17 |  | LSPE, LSG
12/12/1972 –9/30/1977 |

## PDP-15 Setup to Process PSE Data at UTMB in Galveston, ca. 1977

## Lunar Seismic Data Tape Storage at UT-MSI in Galveston

## Sample Compressed Seismograms

- [from Nakamura et al., *Proc. LPSC* **5th**, 2883-2890, 1974]

## Front View of the Moonwith Apollo Stations and EpicentersRed: Shallow MQGreen: Deep MQ

## Interior Cross-Section of the Moon

- [from Nakamura et al., JGR 87 Suppl., A117-A123, 1982]

## More reliable estimates of seismic velocity distribution1. MCMC inversion

**2. Receiver function**
**3. Seismic noise correlation**

## Seismic Velocity Profile to 1000 km depth

**Seismic Velocity Profile to 1000 km depth**

**Seismic Velocity Profile**
**by **
**MCMC Inversion**

- [From Khan and Mosegaard, *JGR* **107**, 10.1029/2001JE001658, 2002]

## Apollo 17LSPEConfigurationwith4 Geophones

- [From LaRose et al., *GRL* **32**, L16201, doi:10.1029/2005GL023518, 2005]

## Rayleigh Wave Dispersion and Inferred Subsurface Shear Wave Velocity Distribution

## A New Look at Deep Moonquakes1. A computer search for more deep moonquakes in the Apollo data set

## ProcessingSequence:

- (Raw PSE Data)
- |
**[De-Glitch and Filter]**
- |
**[Event Detection]**
- |
- (800±800 (~6 min.) samples)
- |
**[Waveform Cross-Correlation]**
- |
- (Set of Cross-Correlation Coefficients)
- |
**[Single-Link Cluster Analysis]**
- |
- (Initial Groups of Events)
- |
**[Identification of Subgroup Centers]**
- |
**[Stacking of Subgroup Members]**
- |
- (Reference Waveforms)
- |
**[Cross-Correlation with Entire Data Set]**
- |
- (Final Groups of Matched Events)

## Waveform Cross-Correlation

## Single-Link Cluster Analysis

## Sample Distribution of Cross-Correlation Coefficient Between Two Arbitrary A-Events

## Numbers of deep moonquake events and nests – old & new

|  | 
Original Catalog | 
New Total |
| --- | --- | --- |
| 
Number of Events | 
1360 | 
7245 |
| 
Number of Nests | 
108 (77) | 
317 |

## An Example of Deep Moonquake Waveform Stacking to Enhance Signal-to-Noise Ratio

## Deep Moonquake Epicenters

**Green: Old**
**Red: New**

**Deep Moonquake Epicenters**

## New Horizons LEISA Thermal Emission Images of Io

- [from Spencer et al., Science 318, 240-243, 2007]

## 2. Any more far-side deep moonquakes?

## Stacked Seismograms Displaying Missing S-wave Arrivals at Certain Stations

## Limiting Rays to

**Limiting Rays to**
**Apollo Seismic Network**

**Lunar Far-Side Zones**
**as Defined by the Apollo Network**

## Two Hypotheses to Explain 

**Two Hypotheses to Explain **
**No Deep Moonquake Detection from Zone D **

## 3. DMQ nest size and geometry

## Stacked A1 Seismogramswith P and S windows for analysis indicated

## Phase spectrum: () = tan-1[QSP()/CSP()]

- QSP(**) = quadrature spectrum = *Im*{*P*(**)}
- CSP(**) = co-spectrum = *Re*{*P*(**)}
*P*(**) = cross-power spectrum of
- waveforms *A*(*t*) and *B*(*t*)
- If *B*(*t*) = *k* *A*(*t* - **)  then
**(**) = ** + [1 - sgn(*k*)]/2
- d**(**) /d**
******when *k *>0; =  when *k *<0

## Examples of Coda-wave Cross-Phase SpectraLeft - in phase;                 Right - opposite phase

## A1 Hypocenter Locations Relative to Reference Event (1976/076)blue: normal polarity     red: inverted

## What Causes Deep Moonquakes?

-  There is a clear correlation between the occurrence of deep moonquakes and tides raised by Earth and the Sun.
-  Is the tide alone sufficient to cause deep moonquakes?
-  Or, is accumulated tectonic strain necessary?

## How Tides are Generated on the Moon

- The Moon’s orbit is tilted from the ecliptic
- The Moon ‘nods’
- every 27.21 days              (Draconic or nodic month)

- The Moon’s orbit around Earth is non-circular
- The Moon ‘shakes head’
- every 27.55 days     (Anomalistic month)

## Lunar Monthly Phases, 

**Lunar Monthly Phases, **
**All Deep Moonquakes**

## Monthly Phases of Deep Moonquake Occurrence (Polarities as indicated)

**Monthly Phases of Deep Moonquake Occurrence **(Polarities as indicated)

## Slide 39

## Epicenter Location vs. Monthly Occurrence Pattern

**Epicenter Location vs. Monthly Occurrence Pattern**

- Near Apogee	Near Perigee	Weakly Anomalistic